What is Scar Endometriosis? Symptoms, Causes, Risks and Treatment

What Is Scar Endometriosis?

Scar endometriosis is a rare form of endometriosis that occurs when endometrial-like tissue grows in or near a surgical scar, most often on the abdominal wall. It is most commonly reported after caesarean section, but can also occur after other uterine or pelvic operations such as hysterectomy, myomectomy, or laparoscopic procedures.

It is uncommon and generally develops after surgery, such as a caesarean section. Studies report that it arises in approximately 0.03-3.5% of women who have had a caesarean delivery, highlighting how rare the condition is.

This tissue behaves similarly to the lining of the womb, responding to hormonal changes during the menstrual cycle. As a result, it can become swollen and painful around the time of periods, sometimes causing a tender lump at the scar site and, in some cases, changes in colour or bleeding from the scar.

In some cases, scar endometriosis may occur alongside pelvic endometriosis, which may require further evaluation.

Also Read: What is Endometriosis?

How Does Scar Endometriosis Develop?

Scar endometriosis is thought to develop when endometrial cells are accidentally implanted into the wound during surgery. Since symptoms can appear much later, it is not always easy to link them back to a past surgery. During procedures such as a caesarean section, endometrial cells may be transferred via instruments, gloves, or amniotic fluid and can become trapped in the incision as it heals.

Once inside the scar tissue, these cells can survive and respond to natural hormones, particularly oestrogen. Over time, they may grow and form a small nodule or mass in the abdominal wall or surrounding tissues. Since menstrual hormones influence scar endometriosis, symptoms may not appear until months or even years after surgery.

What Are Symptoms of ScarEndometriosis?

The most common symptom of scar endometriosis is pain at or near the surgical scar, especially pain that worsens in a cyclical pattern around your period. Many people describe a lump or swelling in the scar that feels more tender and may enlarge during menstruation.

Other possible symptoms include:

• A noticeable lump near or within the scar that may feel firm to the touch.
• Swelling or a thicker area around the scar that may become more obvious over time.
• Changes in skin colour over the lump in some cases.
• In rare situations, bleeding or a brownish discharge from the scar during your period.
• Symptoms similar to endometriosis, such as painful periods or ongoing pelvic pain, are especially common if pelvic endometriosis is also present.

Scar endometriosis is often misdiagnosed initially because its symptoms can mimic those of hernias, lipomas, or other scar tissue issues. A key sign is a history of surgery combined with a painful lump that worsens during the menstrual cycle.

Is Scar Endometriosis Dangerous?

Scar endometriosis is usually not life-threatening, but it can cause severe pain. This condition can significantly impact daily life. Many individuals question its severity and whether they should be concerned.

The main concern in most cases is ongoing pain, limitation in daily activities, and the possibility of the lesion gradually increasing in size over time.

For many people, the pain can interfere with walking, exercise, lifting, sleep, intimacy, or caring for a baby after a caesarean. In some cases, scar endometriosis can lead to dense scar tissue (fibrosis) in the abdominal wall, which can make surgery more complex if treatment is delayed. Infection is uncommon but can occur, particularly if the scar is ulcerated or discharging.

Can Scar Endometriosis Turn Into Cancer?

Malignant (cancerous) change in scar endometriosis is rare, but it has been documented in the medical literature. When it occurs, the most commonly reported cancer types are clear cell carcinoma and endometrioid carcinoma arising in a long-standing abdominal wall endometriosis lesion.

Cancer arising from abdominal wall endometriosis is extremely rare and represents only a very small proportion of endometriosis-related cancers. In such cases, the disease tends to appear several years after the initial surgery as a rapidly growing, painful lesion, with possible skin involvement. 

Given the very small number of reported cases, experts emphasise that scar endometriosis is generally benign. However, any noticeable changes in size, shape, or behaviour of a scar-area lump should be evaluated promptly.

How is Scar Endometriosis Diagnosed?

Diagnosis is based on a combination of your history, physical examination, and imaging tests, with final confirmation by microscopic examination of tissue.

Your doctor may:

• Ask about your surgical history, especially caesarean sections or gynaecological operations.
• Explore whether your scar pain or swelling follows a cyclical pattern with your periods.
• Examine the scar area for a tender lump, thickening, or skin changes.
• Arrange imaging, such as ultrasound, which can often identify an abdominal wall mass suggestive of endometriosis.
• In some cases, request an MRI to better understand the size and depth of the lesion before surgery.

Definitive diagnosis is usually made after surgical removal of the mass, when a pathologist confirms the presence of endometrial-type tissue in the scar. This also helps rule out other causes such as hernias or tumours.

What Are Scar Endometriosis Treatment Options?

The main treatment for scar endometriosis is surgical removal of the affected tissue. Medicines can reduce symptoms in some cases, but they rarely completely remove the lesion.

Common approaches include:

• Wide Local Excision

  Surgeons usually recommend removing the nodule with a margin of healthy tissue, often at least 1 cm, to reduce the risk of recurrence. If the lesion involves deeper layers or muscle, a larger section of the abdominal wall may need to be removed and repaired, sometimes with mesh reinforcement.

• Hormonal Treatment

  Hormonal therapies such as combined oral contraceptives, progestogens, or gonadotropin-releasing hormone (GnRH) analogues can help reduce pain and temporarily shrink lesions by lowering or modifying hormone stimulation. However, symptoms often return when medication is stopped, so surgery remains the only curative option for most cases.

• Other Minimally Invasive Options

  In a few reports, methods such as cryoablation or injection of alcohol into the lesion have been tried, but these are less established than surgical excision. Alongside these treatments, pain-relief medicines such as non-steroidal anti-inflammatory drugs (NSAIDs) can help manage discomfort before and after surgery.

What is the Outlook and Recurrence Risk Of Scar Endometriosis?

The outlook for scar endometriosis is generally good when it is accurately diagnosed and completely removed. Many people report significant or complete relief of their pain after surgery, with a return to normal daily activities.

Recurrence is relatively uncommon, especially when the lesion is completely removed with clear margins. Some studies report recurrence rates of 1-5%, suggesting that many cases are effectively treated with a single operation. Recurrence is more likely when excision is incomplete or microscopic disease persists.

In general, a follow-up period is recommended, especially when the lesion has been present for an extended period or shows any irregularities.

When Should You See A Doctor?

You should consider seeing a doctor if you notice a painful lump, swelling, or unusual change in or near a surgical scar, especially if the discomfort gets worse around your period. 

This is particularly important if you have previously had a caesarean section or pelvic surgery involving the uterus or ovaries.

Seek prompt medical advice if:

• The scar lump is growing or becoming more painful.
• You notice discolouration, discharge, or bleeding from the scar, especially in a cyclical pattern.
• Pain around the scar is affecting your ability to work, care for your family, or carry out daily activities.
• You have general endometriosis symptoms alongside a suspicious scar lump, such as severe period pain or chronic pelvic pain.

Early assessment can help ensure timely diagnosis and treatment, reducing the risk of long-term pain or more complex surgery later on.

Takeaway

Scar endometriosis is a rare but important cause of pain and lump formation at the site of previous surgical scars, most commonly after a caesarean section or other gynaecological surgery. When asking, “Is scar endometriosis dangerous?”, the key takeaway is that it is usually benign, but it should not be ignored as it can cause persistent pain and, in very rare cases, may undergo malignant change.

The most effective treatment is wide excision surgery, which offers a good prognosis and low recurrence risk when the lesion is completely removed. Hormonal treatments and pain relief medicines may help manage symptoms, but they do not provide a definitive cure.

The most important step is not to delay in evaluation. If you notice a painful or changing lump near a scar, early medical assessment can help confirm the diagnosis and guide the right treatment.