This page is supervised by specialist physicians at IC Clinic Shibuya, located a 3-minute walk from JR Shibuya Station.
💬「My epidermoid cyst is red, swollen, and painful!」
💬「Pus is coming out and it smells!」
Are you experiencing these symptoms?
This may be an inflamed epidermoid cyst. Because leaving it untreated is likely to make it worse, prompt and appropriate treatment is important.
An inflamed epidermoid cyst (atheroma) is one in which bacteria have entered an existing cyst, causing inflammation and suppuration.
As symptoms worsen from an ordinary epidermoid cyst to an inflamed one, pain develops, making prompt treatment—rather than leaving it untreated—important.
This article introduces the characteristics, causes, and treatment options for inflamed epidermoid cysts in the Tokyo (Shibuya) area.
Even if you are concerned that you may have an inflamed epidermoid cyst, we explain clearly and carefully how to approach treatment, so please use this as a reference.
🏥 What Is an Inflamed Epidermoid Cyst (Atheroma)? Symptoms and Causes
An inflamed epidermoid cyst (atheroma) refers to a condition in which bacteria have entered the sac-like cyst beneath the skin, resulting in inflammation and suppuration [1,2].
In its early stages, an epidermoid cyst causes little to no pain and is felt only as a lump when touched, but once inflammation develops it becomes red and swollen, and pain sets in [2,3].
This condition is referred to as an inflamed epidermoid cyst or a suppurative epidermoid cyst.
※ For the remainder of this article, the term “inflamed epidermoid cyst” will be used consistently.
⚠️ Risks of Leaving an Epidermoid Cyst (Atheroma) Untreated: Suppuration and Odor
If an epidermoid cyst is left untreated, the sebum and keratin inside can decompose, allowing bacterial infection to progress and triggering inflammation and suppuration [1,3].
As inflammation advances, the area becomes red and swollen with intense pain, and pus accumulates, creating a boil-like condition. Furthermore, if the sac ruptures and its contents are discharged, there is a risk that inflammation spreads to the surrounding tissue and progresses to cellulitis or other serious infections [2,4].
In addition, as the contents of the sac decompose, they can produce a strong, unpleasant odor, which not infrequently interferes with daily and social life [5].
- 🔴 Progression of Inflammation and Suppuration:
The interior of an epidermoid cyst sac is an environment where dead skin cells and sebum accumulate easily, making it highly conducive to bacterial growth.
In particular, when bacteria enter through the “punctum”—the opening connected to the skin surface—infection can spread rapidly and trigger inflammation.
Once inflammation occurs, the cyst becomes red and swollen and is accompanied by intense throbbing pain.
As it worsens further, pus accumulates inside, creating a boil-like state, and the area feels warm to the touch, with the skin surface becoming raised. - 👃 Development of Odor:
The old keratin and sebum that accumulate inside the sac are broken down by bacterial action, producing a distinctive unpleasant odor.
This odor can become strong enough to be noticeable not only to oneself but also to those nearby, causing psychological distress in daily and social settings. - 💥 Rupture and Increased Complexity of Treatment:
When suppuration progresses and the internal pressure reaches its limit, the cyst may rupture spontaneously, releasing pus and decomposed contents.
While pain may ease temporarily, the ruptured wound becomes more susceptible to further bacterial entry, risking the spread of inflammation to surrounding skin and potentially causing cellulitis—a widespread skin infection.
Moreover, a ruptured cyst tends to adhere more easily to surrounding tissue, making subsequent surgery more complex and increasing the likelihood that scarring will remain. - 🎈 Enlargement:
Repeated episodes of inflammation and rupture can cause the cyst sac to grow even larger, compress surrounding tissue, and become visibly prominent as a large lump.
The larger it becomes, the wider the surgical area required, which also affects the cost and recovery period.
As described above, leaving an epidermoid cyst (atheroma) untreated is not merely a cosmetic concern—it increases the risk of pain and odor, as well as more serious infections, and may make treatment more complex.
For this reason, if you notice symptoms of an epidermoid cyst, it is important to seek medical attention promptly and receive appropriate treatment.
🚫 Never Attempt to Squeeze or Pop an Epidermoid Cyst (Atheroma) Yourself
Attempting to pop an epidermoid cyst yourself carries a significant risk of worsening infection and inflammation and must be absolutely avoided [2,3].
Trying to squeeze it with unclean hands or fingernails allows bacteria to enter the interior and promotes inflammation. Furthermore, if the sac ruptures and its contents spread to the surrounding tissue, inflammation intensifies and pain and swelling worsen [1,3].
Additionally, if the sac remains, recurrence is likely, and repeated episodes can make treatment more difficult. Definitive treatment requires complete surgical removal of the sac at a medical facility [1,4].
Attempting to pop an epidermoid cyst yourself can lead to the following problems.
- 🦠 Increased Risk of Bacterial Infection:
Attempting to pop a cyst using fingers, fingernails, or an unsterile needle damages the skin, greatly increasing the likelihood that large numbers of bacteria enter the interior of the cyst sac.
This can cause inflammation to worsen further, promote suppuration, and increase the risk of cellulitis or other serious infections in the surrounding skin. - 💢 Worsening Inflammation and Increased Pain:
Forcibly popping the cyst can cause the internal sac to rupture, with its contents spreading to surrounding tissue and triggering a strong inflammatory reaction.
This can further worsen symptoms such as severe pain, swelling, and warmth, and significantly interfere with daily life. - 🩹 Scar Formation:
When inflammation or infection becomes severe, noticeable scarring tends to develop during the healing process.
On visible areas such as the face, this can become a cosmetic concern. - 🔄 Risk of Recurrence:
The fundamental treatment for an epidermoid cyst is complete surgical removal of the sac—not just its contents.
Even if you pop it yourself, if any part of the sac remains, contents will re-accumulate over time and recurrence is very likely.
Repeated recurrences can also make treatment more difficult. - ⏰ Delayed Diagnosis:
Attempting self-treatment may delay seeking medical attention.
While rare, malignant tumors that resemble epidermoid cysts in appearance do exist.
A consultation with a specialist enables an accurate diagnosis and the development of an appropriate treatment plan.
Epidermoid cysts (atheromas) require appropriate treatment by a dermatologist or plastic and reconstructive surgeon.
If you notice any concerning symptoms, please do not attempt to handle them yourself—seek medical attention promptly.
A specialist will recommend the most suitable treatment approach based on the presence of inflammation, the size of the cyst, and its current condition.
📈 Why Epidermoid Cysts (Atheromas) Grow Larger — Causes and What to Do
Once an epidermoid cyst (atheroma) forms, it almost never resolves on its own and in most cases gradually enlarges over time.
The primary reason for this growth is the continuous accumulation of old keratin and sebum that are constantly produced inside the sac.
- 📊 Continuous Production of Contents:
The epidermoid cyst sac is formed from an inverted portion of the skin.
As a result, the cells lining the inside of the sac continue to produce keratin just like normal skin.
The ongoing accumulation of this keratin and sebum inside the sac causes the cyst to gradually expand. - 🔁 Repeated Inflammation:
When an epidermoid cyst becomes inflamed, the surrounding tissue swells and the cyst itself may temporarily feel larger.
Even after the inflammation subsides, contents re-accumulate, and each subsequent episode of inflammation can lead to further enlargement in a vicious cycle.
Repeated inflammation tends to cause the sac wall to thicken and adhere to surrounding tissue, contributing to further growth. - 👔 Irritation and Friction:
Chronic irritation from clothing rubbing against the cyst, physical pressure, or compression can make the cyst more prone to inflammation, which may in turn cause it to enlarge.
💡 What to Do When an Epidermoid Cyst (Atheroma) Has Grown Larger
As an epidermoid cyst grows larger, not only do symptoms such as pain and odor become more pronounced, but cosmetic concerns and everyday inconveniences also increase (e.g., catching on clothing, getting in the way when sitting).
Furthermore, the larger it grows, the wider the surgical incision required, and scarring becomes more likely.
Therefore, if you feel that your epidermoid cyst (atheroma) has grown larger, it is important to consider the following points and seek medical attention promptly.
- 🏥 Early Consultation with a Specialist:
Epidermoid cysts are easier to treat when they are still small, with less surgical burden and less noticeable scarring.
Before it grows larger, consult a specialist such as a dermatologist or plastic and reconstructive surgeon for an accurate diagnosis and discussion of appropriate treatment. - 🔪 Considering Appropriate Surgery:
The definitive treatment for an epidermoid cyst is surgery to completely remove the sac—not just its contents.
Performing surgery when the cyst is not inflamed is ideal.
If inflammation is present, the first step is to address the inflammation (e.g., incision and drainage), after which surgical removal of the sac is considered. - ⛔ No Self-Treatment or Self-Diagnosis:
A larger cyst has even greater internal pressure, so attempting to pop it yourself significantly increases the risk of more serious infection or inflammation.
Please never touch or attempt to pop it on your own.
Every person’s cyst differs in size and condition.
Receiving a specialist’s diagnosis and choosing the most appropriate treatment for your situation is the first step toward a safe and effective resolution.
🔍 Symptoms of an Inflamed Epidermoid Cyst
When an epidermoid cyst becomes inflamed or suppurated, it turns red and swollen, and pain develops.
In cases of severe suppuration, the sac-like structure beneath the skin is disrupted and pus accumulates inside.
This condition is also referred to as an abscess and is accompanied by intense pain.
🔬 Medical Causes of Inflammation in Epidermoid Cysts
Epidermoid cysts have a small opening known as the “punctum,” and bacteria entering through this opening is the primary cause of inflammation [1,2].
An epidermoid cyst is a benign tumor formed by the accumulation of keratin and sebum beneath the skin, but because the interior of the sac contains no immune cells, it is highly susceptible to bacterial infection [3,5].
As a result, even minor irritation or friction can trigger bacterial infection, potentially leading to an inflamed epidermoid cyst [2,4].
(※ See also: What Is an Epidermoid Cyst?)
The interior of an epidermoid cyst sac has a structure that contains no cells responsible for immune function (i.e., the ability to eliminate bacteria and other pathogens that enter the body), making it vulnerable to bacterial infection.
In particular, repeatedly touching or attempting to pop the cyst can introduce bacteria and cause an inflamed epidermoid cyst to develop, so please try to avoid touching it as much as possible.
🧠 Psychological Causes of Inflammation in Epidermoid Cysts
The “psychological complacency” of thinking “It’s just a lump, so I can leave it alone” or “It’s a benign tumor, so it should be fine to ignore it” can also be a contributing factor in the development of an inflamed epidermoid cyst.
As mentioned above, epidermoid cysts do not resolve on their own and are susceptible to bacterial infection.
Nevertheless, some patients leave the cyst untreated and only seek medical attention once inflammation and pain develop.
We strongly encourage everyone reading this article to never leave it untreated and to contact a medical facility capable of treating epidermoid cysts as soon as possible.
⚠️ [Important] Visit a Clinic Before Your Inflamed Epidermoid Cyst Ruptures
An inflamed epidermoid cyst has progressed beyond an ordinary cyst and carries greater risks.
Touching it carelessly can cause it to rupture, so please visit a clinic for evaluation before that happens.
In fact, there are hidden risks of rupture even in everyday life with an inflamed epidermoid cyst.
Below, we look at the causes of rupture and what to do if the contents discharge.
Knowing this information can help you prevent worsening symptoms from a rupture before you are able to seek treatment.
💥 Causes of Rupture in an Inflamed Epidermoid Cyst
An inflamed epidermoid cyst can rupture with even a minor impact.
Once bacteria infect an epidermoid cyst and it becomes inflamed, the sac-like structure becomes fragile and prone to tearing.
What initially felt like a firm lump gradually has its overlying skin soften as inflammation progresses, and when touched, it becomes noticeably warm.
Once it has softened, even slight pressure or contact can cause it to rupture and pus to discharge.
If the sac ruptures, pus spreads to the surrounding area and inflammation worsens further.
The area becomes red and swollen, and as the condition progresses, the opening also breaks down and widens, discharging malodorous pus and the contents of the sac.
This state in which pus is discharged spontaneously is referred to as “spontaneous rupture.”
🏥 What to Do If Your Epidermoid Cyst Ruptures and Discharges Its Contents
If a cyst ruptures and its contents discharge during daily life, please seek medical attention as soon as possible.
In cases of severe suppuration, a procedure may be performed in which the skin is incised and the accumulated pus is drained (incision and drainage).
Because this involves surgical intervention, it is advisable to visit a hospital or clinic with substantial experience in epidermoid cyst surgery.
📞 If You Have Popped Your Cyst Yourself, Please Consult IC Clinic
If you touched your epidermoid cyst and it ruptured, leaving the area red and swollen, please contact IC Clinic right away.
Inflamed epidermoid cysts are prone to leaving scars, so treatment as early as possible is advisable.
We can suggest treatment options designed to minimize discomfort and reduce the visibility of scarring, so you can feel at ease in our care.
Our epidermoid cyst surgery is also covered by Japanese public health insurance, so you can feel reassured about the cost.
Procedures are typically completed in around 20 minutes at most, so same-day discharge is generally possible.
If you have any concerns about an epidermoid cyst, please do not leave it unaddressed—contact IC Clinic for a consultation.
🔪 Treatment for Epidermoid Cysts (Atheromas) | Complete Surgical Removal as the Standard Approach
For an inflamed epidermoid cyst, the first step is a procedure to reduce the inflammation (incision and drainage, or antibiotic therapy), followed by surgical removal of the entire sac [1,2,3].
Definitive treatment is complete surgical removal of the sac; removing only the contents is known to carry a high likelihood of recurrence [1,4].
The main surgical techniques are “fusiform excision” and “punch excision (punch-out method),” with the physician selecting the most appropriate technique based on the size of the cyst and the presence or absence of inflammation [2,4].
📋 Surgical Techniques for Epidermoid Cysts (Atheromas): Punch Excision (Punch-Out Method) and Fusiform Excision
There are two main surgical techniques for treating an epidermoid cyst (atheroma): “punch excision (punch-out method)” and “fusiform excision.”
The choice of technique is determined by the physician based on factors such as the size, location, and presence or absence of inflammation.
| Surgical Technique | Features (Advantages) | Disadvantages / Points to Note | Indications |
| Punch Excision (Punch-Out Method) | ・Minimal scarring: Because the contents and sac are removed through a small opening of just a few millimeters in diameter, the resulting scar is less noticeable. ・Faster recovery: Little or no suturing is required, so post-operative swelling and pain tend to be minimal and the healing period shorter. ・Less physical burden: The procedure is completed quickly and requires only local anesthesia. | ・Not suitable when inflammation is present: When inflammation is significant or suppuration has occurred, the sac becomes fragile and complete removal may not be possible, so this technique is often not selected. ・Recurrence risk: In rare cases, a small portion of the sac may remain, resulting in recurrence. ・Requires skill: Precise removal of the sac through a small opening demands a high level of surgical expertise. | ・Cysts without inflammation: Stable cysts with no redness or pain. ・Relatively small cysts: Most commonly indicated for cysts up to approximately 2 cm in diameter, though larger cysts may also be suitable depending on the surgeon’s skill. ・Particularly recommended for cysts in cosmetically sensitive areas such as the face or neck where minimal scarring is desired. |
| Fusiform Excision | ・Reliable removal: Because a larger incision is made, the entire sac can be visualized and removed with certainty, leaving little residual tissue and resulting in a very low recurrence risk. ・Applicable even when inflammation is present: Even in cases of significant inflammation or suppuration, it is sometimes possible to incise, drain the pus, and remove the sac at the same time (though in severe cases, drainage may be performed first with definitive removal at a later date). ・Very low recurrence risk: Because the sac can be completely removed, the risk of recurrence is very low. | ・Scarring: A larger incision is required proportional to the cyst size, so scarring tends to be more prominent compared with punch excision. ・Longer recovery: Suturing is usually necessary, and time is required for suture removal and wound healing. ・Slightly greater physical burden: Performed under local anesthesia, but more invasive than punch excision. | ・Inflamed cysts: Cysts that are red, swollen, or filled with pus. ・Larger cysts: Cysts with a diameter of approximately 3 cm or more, or those located deep beneath the skin. ・Cases where punch excision is not feasible, or where the cyst has ruptured and adhered to surrounding tissue. |
🎯 What Is the Punch Excision (Punch-Out Method) for Epidermoid Cysts (Atheromas)?
The “punch excision,” also known as the “punch-out method,” is a surgical technique in which the small opening (punctum) at the center of the epidermoid cyst (atheroma)—or a newly created small incision—is used as the entry point, through which the cyst sac is extracted using a specialized instrument in a coring motion.
Procedure steps:
1. Local anesthesia: Local anesthetic is first injected into the cyst and the surrounding area.
2. Small incision or puncture: A small opening approximately 2–5 mm in diameter is made at the punctum or at a new site.
3. Discharge of contents: Pressure is applied through the small opening to expel the accumulated keratin, sebum, and other contents from inside the cyst.
4. Removal of the cyst wall: After the contents have been expelled, the sac (cyst wall) is carefully peeled away from surrounding tissue using specialized forceps and completely removed.
Care is taken throughout this process to avoid rupturing the sac.
5. Completion: Once complete removal of the sac is confirmed, the wound is generally left to heal naturally without suturing.
In some cases, a small number of sutures may be placed.
The wound is small and typically closes within a few days.
Advantages:
・Cosmetic: The primary advantage is that the resulting scar is very small and less noticeable.
It is particularly suitable for cosmetically sensitive areas such as the face and neck.
・Less physical burden: The procedure is short (typically 10–20 minutes) and involves minimal blood loss, placing less burden on the patient.
・Faster recovery: Because the wound is small, post-operative swelling and pain are minimal and return to daily activities is prompt.
Points to note:
Punch excision is suitable for non-inflamed, relatively small epidermoid cysts.
When inflammation is significant or suppuration has already occurred, the sac becomes fragile, making complete removal difficult, and fusiform excision is often selected instead.
✂️ What Is Fusiform Excision for Epidermoid Cysts (Atheromas)?
“Fusiform excision” is the most reliable surgical technique, in which the skin directly overlying the epidermoid cyst (atheroma) is directly incised and the entire cyst sac is removed under direct visualization.
Procedure steps:
1. Local anesthesia: Local anesthetic is injected into the cyst and surrounding area.
2. Skin incision: The skin is incised in a fusiform (leaf-shaped) pattern along the long axis of the cyst, sized appropriately to the cyst.
3. Dissection and removal of the cyst wall: The cyst sac (cyst wall) is carefully dissected from the surrounding tissue through the incision and completely removed.
Care is taken throughout to avoid rupturing the sac.
4. Hemostasis and closure: Bleeding is controlled and the skin is carefully sutured. The skin surface is typically closed with sutures.
5. Completion: The wound is covered with gauze or tape for protection.
A follow-up visit for suture removal will be required at a later date.
Advantages:
・Reliability: The primary advantage is that, because the entire sac can be visualized and removed, residual tissue is minimized and the risk of recurrence is very low.
・Broad applicability: The technique can address a wide range of conditions, including inflamed cysts, suppurated cysts, large cysts, and cysts of complex shape.
When inflammation is significant, a two-stage approach may be taken: first incising to drain the pus, then performing definitive removal once the inflammation has settled.
Points to note:
Because fusiform excision involves a larger incision than punch excision, scarring tends to be more noticeable.
Particularly in visible areas such as the face, the shape and length of the scar may require consideration as a cosmetic concern.
Additionally, the post-operative recovery period tends to be somewhat longer than with punch excision.
The choice of technique is determined by thorough discussion with your physician, taking into account the condition of the patient’s cyst and their preferences regarding scarring.
🏠 Is Same-Day Discharge Surgery Possible for Epidermoid Cysts (Atheromas)?
Most epidermoid cysts (atheromas) can be treated as day surgery, allowing same-day discharge.
This is because the procedure itself is performed under local anesthesia and completed in a relatively short time.
- ✅ Typical cases:
For small, stable cysts without inflammation, surgery can be performed under local anesthesia on an outpatient basis and patients can return home the same day.
Procedure time varies depending on the size and number of cysts and the technique selected, but it generally takes around 10 to 30 minutes.
After the procedure, patients receive basic wound care and post-operative instructions, and can return home directly. - 👍 Advantages of same-day discharge surgery:
- Less time burden: Because no hospitalization is required, the impact on daily life and work is minimized.
- Less psychological burden: Patients do not need to spend time in an unfamiliar hospital environment and can recover comfortably at home, reducing psychological stress.
- Less financial burden: No hospitalization fees are incurred, which helps keep overall medical costs lower.
- ⚠️ Exceptional cases (where hospitalization may be required):
However, not all epidermoid cysts (atheromas) can be managed with same-day discharge. The following situations may require hospitalization or more careful planning.- Very large cysts: For very large cysts measuring several centimeters or more in diameter, there is a greater possibility of significant blood loss and more complex post-operative care, so hospitalization for observation may be required.
- Severely inflamed or suppurated cysts: When a cyst has formed an abscess with severe inflammation, drainage may be performed first, with definitive removal scheduled a few days later. Depending on the post-operative condition, a short hospital stay may be necessary.
- Patients with unstable general health: Patients with serious underlying conditions (such as heart disease or diabetes) may be advised to undergo inpatient surgery in a more controlled environment given the surgical risks involved.
- Cysts in special locations: When the surgical difficulty is high—for example, cysts near joints or close to important blood vessels or nerves—a more cautious approach is required.
In principle, same-day discharge is generally possible, but the final determination is made by the physician based on the patient’s condition and medical history.
At your consultation, please ask in detail whether same-day discharge surgery is an option for your case.
💰 How Much Does Epidermoid Cyst (Atheroma) Surgery Cost? Health Insurance Coverage
When considering surgery for an epidermoid cyst (atheroma), many patients are concerned about the “cost.”
Because epidermoid cyst surgery is in principle covered by Japanese public health insurance, the out-of-pocket expense is relatively manageable.
Below, we explain the approximate cost of surgery and details regarding insurance coverage.
💴 Approximate Cost of Epidermoid Cyst (Atheroma) Surgery
The cost of epidermoid cyst (atheroma) surgery varies depending on the size and location of the cyst, the presence or absence of inflammation, and the surgical technique selected.
Separate fees may also apply for the initial or follow-up consultation, tests, anesthesia, and medication.
The following provides a general guide to approximate surgical costs with health insurance (30% patient co-payment).
| Cyst Size / Condition | Approximate Surgery Cost (30% co-payment) | Notes |
| Small (under 3 cm in diameter, no inflammation) | Approx. ¥5,000–¥10,000 | ・Punch excision or small incision technique is most commonly used. ・The lowest-cost scenario. ・Initial consultation fee, examination fee, local anesthesia, prescription medications (antibiotics, pain relief, etc.), and post-operative wound care fees may be charged separately. |
| Medium (3 cm to under 5 cm in diameter, no inflammation) | Approx. ¥10,000–¥15,000 | ・Fusiform excision is most commonly selected. ・Cost is higher than for small cysts due to the wider surgical area. ・Pathological examination fees may be added in some cases. |
| Large (5 cm or more in diameter, no inflammation) | Approx. ¥15,000–¥25,000 | ・Fusiform excision is almost always required. ・Cost is higher due to increased surgical complexity and time. ・Pathological examination fees are nearly always applicable. |
| Inflamed or suppurated cysts | Inflammation management procedure: Approx. ¥3,000–¥5,000 Definitive surgery (at a later date): above amounts plus applicable surgery cost by size | ・When suppuration is present, incision and drainage is performed first. ・This procedure itself incurs a fee, and definitive removal of the sac is subsequently required, so total costs tend to be higher. ・In cases of severe inflammation, additional follow-up visits may be needed, which increases consultation and treatment fees. |
[Important Notes]
・The costs listed above are estimates only and may vary depending on the medical facility, region, and specific treatment content.
・In most cases, separate fees will apply in addition to the surgery cost, including initial or follow-up consultation fees, examination fees (e.g., pathological examination), anesthesia, prescription medications (antibiotics, pain relief, antiseptic, etc.), and post-operative wound care fees.
Including these fees, the total amount may be higher than the estimates above.
・Depending on your health insurance association or municipality, high-cost medical expense benefits or medical fee subsidy programs may be available—please check whether these apply to you.
・For accurate cost information, please contact the medical facility you wish to visit directly, or confirm with the physician or reception staff at your consultation.
🏥 Is Epidermoid Cyst Surgery Covered by Health Insurance?
To state the conclusion first, epidermoid cyst (atheroma) surgery is in most cases covered by Japanese public health insurance.
This is because an epidermoid cyst is medically classified as a “benign skin tumor” and, given the risk of inflammation and infection, is considered a condition requiring treatment.
This means patients can receive surgery at the co-payment rate applicable to their health insurance (typically 30%, 10%, or 20%).
✅ Cases Covered by Health Insurance:
・When medical treatment is deemed necessary:
- The cyst has grown and is interfering with daily life (e.g., rubbing against clothing, causing pain when sitting).
- The cyst is inflamed or suppurated.
- There is pain or an unpleasant odor.
- The patient is concerned about the appearance but the physician has determined that medical treatment is necessary.
❌ Cases That May Not Be Covered by Health Insurance:
・When deemed purely cosmetic in nature:
- If the cyst is very small, entirely asymptomatic, and the medical necessity for treatment is low, and the patient’s sole motivation is cosmetic improvement (“I just want to make it look better”), the procedure may be classified as non-insured (self-pay).
In such cases, it becomes “private pay (self-funded)” and the full cost is borne by the patient.
However, since most epidermoid cysts (atheromas) are considered medically treatable given the future risk of inflammation and cosmetic changes, cases classified as purely cosmetic are relatively uncommon.
📄 Diagnostic Documentation and Pathological Examination:
When surgery is performed under health insurance, the removed tissue is typically submitted for pathological examination.
This is an important test conducted to confirm whether the cyst is malignant or whether it may represent another skin condition.
The results of this examination formally confirm the diagnosis of “epidermoid cyst (atheroma).”
🔍 The Importance of Confirming with Your Medical Facility:
Before undergoing surgery, always ask the reception or the attending physician “Will this be covered by health insurance?”
In particular, some cosmetic surgery clinics specialize in private-pay (self-funded) treatment, so it is important to confirm this in advance.
Since leaving an epidermoid cyst (atheroma) untreated can lead to inflammation, infection, and other complications, we recommend seeking appropriate treatment under health insurance coverage if you notice any concerning symptoms.
🔪 How Is an Inflamed Epidermoid Cyst Treated?
What happens when an epidermoid cyst becomes inflamed?
The definitive treatment for an inflamed epidermoid cyst is surgery.
Specifically, there are two main surgical techniques: “fusiform excision” and “punch excision (punch-out method).”
Let us look at each treatment option in turn.
🔷 (1) Surgical Technique: Fusiform Excision
Because reducing the inflammation takes priority, an “incision and drainage procedure” is performed before surgery.
“Incision and drainage” refers to a procedure in which a small incision is made in the skin to release the accumulated pus.
Once the inflammation has resolved, definitive surgery to remove the cyst is performed.
The surgical technique itself is straightforward: the skin is incised in a fusiform (spindle) shape, the cyst is removed, and the wound is sutured.
With careful suturing, scarring tends to become less noticeable over time.
For inflamed epidermoid cysts, this approach tends to yield a better post-operative course than attempting punch excision.
🔸 (2) Surgical Technique: Punch Excision (Punch-Out Method)
“Punch excision” is a technique in which a specialized punch-like instrument is used to create a small opening in the cyst, through which the contents are expressed, and then the deflated sac is extracted.
The punch excision technique is generally recognized for features such as “minimal and less noticeable scarring“ and “very short procedure time.”
Even for inflamed epidermoid cysts, same-day discharge surgery using the punch excision technique may be possible depending on the physician’s assessment.
→ For more information about epidermoid cyst (atheroma) surgery, please see ‘What Is an Epidermoid Cyst (Atheroma)? A Guide to Treatment.’
💊 Are Medications Effective for Inflamed Epidermoid Cysts?
In the treatment of inflamed epidermoid cysts, antibiotics may be administered to reduce inflammation.
While antibiotics can relieve pain in some cases, it is important to understand that this simply means the infection causing the pain in the cyst has subsided—the tumor itself has not been removed.
This approach is effective against infection, but on its own it is insufficient as treatment for the cyst itself.
For definitive treatment of an epidermoid cyst, surgical intervention is still necessary.
💰 Treatment Costs for Inflamed Epidermoid Cysts
For the diagnosis, examination, surgery, and pathological examination involved in treating an epidermoid cyst, Japanese public health insurance applies, so please feel reassured.
The following are approximate treatment costs at IC Clinic.
| Approximate Epidermoid Cyst Surgery Costs (30% patient co-payment) | ||
| Exposed areas | Under 2 cm | Approx. ¥5,000–¥6,000 |
| 2 cm to under 4 cm | Approx. ¥11,000–¥12,000 | |
| 4 cm or more | Approx. ¥15,000–¥16,000 | |
| Non-exposed areas | Under 3 cm | Approx. ¥4,000–¥5,000 |
| 3 cm to under 6 cm | Approx. ¥10,000–¥11,000 | |
| 6 cm or more | Approx. ¥12,000–¥14,000 | |
| ※ As there are reports of malignant tumors arising from epidermoid cysts, pathological examination is in principle performed based on the physician’s judgment. ※ In cases of multiple cysts, simultaneous surgery on adjacent sites may be possible in some cases, subject to the physician’s assessment. ※ In addition to the above surgery costs, consultation and prescription fees of approximately ¥1,000, examination fees of approximately ¥1,000, and pathological examination fees of approximately ¥3,000 will also apply. | ||
| Approximate Epidermoid Cyst Surgery Costs (10% patient co-payment) | ||
| Exposed areas | Under 2 cm | Approx. ¥2,000 |
| 2 cm to under 4 cm | Approx. ¥4,000 | |
| 4 cm or more | Approx. ¥5,000 | |
| Non-exposed areas | Under 3 cm | Approx. ¥1,500 |
| 3 cm to under 6 cm | Approx. ¥3,500 | |
| 6 cm or more | Approx. ¥4,500 | |
| ※ From October 1, 2022, patients aged 75 or older with income above a certain threshold will have their out-of-pocket co-payment rate revised. ※ As there are reports of malignant tumors arising from epidermoid cysts, pathological examination is in principle performed based on the physician’s judgment. ※ In cases of multiple cysts, simultaneous surgery on adjacent sites may be possible in some cases, subject to the physician’s assessment. ※ In addition to the above surgery costs, consultation and prescription fees of approximately ¥300, examination fees of approximately ¥300, and pathological examination fees of approximately ¥1,000 will also apply. | ||
❓ Frequently Asked Questions About Inflamed Epidermoid Cysts
Finally, here are some frequently asked questions about epidermoid cysts. Please refer to any sections that concern you.
A. Yes, we recommend seeking medical attention at a clinic even if there is no pain. The cyst has already progressed to mild inflammation, and leaving it unaddressed may cause the redness to intensify, followed by swelling and pain. Even if surgery for removal becomes necessary, addressing it early allows treatment to be carried out with less noticeable scarring. Therefore, if your epidermoid cyst appears red—even without pain—please visit a clinic.
A. Malignant transformation of an epidermoid cyst is extremely rare.
There is no reliable way to distinguish a standard cyst from a malignant one based on symptoms or appearance alone; however, pathological examination of the removed cyst material can determine whether it is malignant.
🏥 For Inflamed Epidermoid Cyst Treatment in Tokyo (Shibuya), Please Consult IC Clinic
This article has introduced the characteristics, causes, treatment options, and costs associated with inflamed epidermoid cysts.
Because an inflamed epidermoid cyst represents a worsening of an ordinary cyst, we encourage you to pursue definitive surgical treatment as soon as possible.
To help reduce the likelihood of post-treatment scarring as much as possible, we recommend not leaving it untreated and coming in for a consultation.
Our clinic can suggest treatment approaches designed to minimize discomfort and reduce scarring, tailored to your symptoms.
If you are troubled by an inflamed epidermoid cyst, please feel free to contact us for a consultation.
✨ Four Features of IC Clinic
👍 (1) We provide specialist treatment focused on outcomes
Experienced specialist physicians deliver results-oriented treatment aimed at minimizing the burden on each patient.
💬 (2) We propose a treatment plan tailored to each patient’s symptoms and wishes
We listen carefully to each patient’s concerns and worries and provide the most suitable treatment plan for their individual needs.
😌 (3) Minimal discomfort, minimal scarring!
From a broad range of treatment options, we select the approach that minimizes discomfort and leaves as little lasting impact as possible after the procedure.
👥 (4) A clinic where anyone is welcome to seek advice, regardless of age or gender
We strive to create a clinic environment where patients of any age or gender feel comfortable seeking a consultation.
📷 Case Studies at Our Clinic
[Case Study] Female patient in her 70s — Treatment of an inflamed epidermoid cyst (atheroma) near the axilla (Updated August 3, 2025)
This patient was a woman in her 70s who presented to IC Clinic Shibuya with a large epidermoid cyst near the right axilla that had become red and swollen, accompanied by tenderness and pus discharge. Following examination, the condition was diagnosed as an inflamed epidermoid cyst with infection. An initial incision and drainage procedure using the punch excision (punch method) was performed to allow the inflammation to settle, after which definitive surgery to remove the cyst sac (cyst wall) was carried out. The wound is now stable with no concern about recurrence, and the patient has returned to a comfortable daily life.
📚 References
1. Japanese Dermatological Association, ed. Dermatology, 11th Edition. Bunkodo, 2018.
2. Zito PM, Scharf R. Epidermoid Cyst. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023.
3. Japanese Dermatological Association. “Clinical Guidelines for Benign Skin Tumors,” 2015.
4. Weedon D. Weedon’s Skin Pathology, 4th Edition. Churchill Livingstone Elsevier, 2016.
5. Morgan MB, Stevens GL, Somach S, Tannenbaum M. Sebaceous cysts: a clinicopathologic and immunohistochemical study of 106 cases. Am J Dermatopathol. 2001;23(5):394-401.
