The excised skin specimen showed foci of endometrial glands surrounded by endometrial stroma, embedded in fibrous scar tissue in the subcutis. Both the glandular epithelium and the stroma showed active proliferation with easily recognizable mitotic figures. A few aggregates of chronic inflammatory cells were associated with some foci of endometrial glands. (Fig 1& 2)

Figure 1

Figure 1: Photomicrograph showing endometriotic glands and stroma embedded in scar tissue (low power)

Figure 2

Figure 2: Photomicrograph showing endometriotic glands and stroma with mitotic figures (arrow and high power)

The proposed theories₈ of endometrioma formation are:

• Retrograde spread of collections of endometrial cells during menstruation

• Blood, lymphatic or iatrogenic spread

• Metaplasia of the pelvic peritoneal cells

• Immune system dysfunction and autoantibody formation

The development of intrapelvic endometriosis may involve retrograde menstruation, maturation of extrauterine primordial cell remnants of embryogenesis, or hematologic or lymphatic spread of endometrial cells. Extrapelvic endometriosis in the lung, skin, and extremities not associated with surgical violation of the uterus is believed to be the result of hematogenous or lymphatic spread of endometrial tissue₉, ₁₀.

Scar endometriomas are believed to be the result of direct inoculation of the abdominal fascia or subcutaneous tissue with endometrial cells during surgical intervention and subsequently stimulated by estrogen to produce endometriomas. This theory is convincingly demonstrated by experiments in which normal menstrual effluent transplanted to the abdominal wall resulted in subcutaneous endometriosis₁₁. In clinical practice, its occurrence has been well documented in incisions of any type where there has been possible contact with endometrial tissue, including episiotomy, hysterotomy, ectopic pregnancy, laparoscopy, tubal ligation, and cesarean section₁₂, ₁₃, ₁₄.

The presence of endometrial tissue can induce metaplasia of the surrounding fascial tissue to form an endometrioma. Alternatively, endometrial cells may reach a caesarean scar via lymphatic or haematogenous routes and subsequently grow into an endometrioma by one of the mechanisms described above. This may cause rare occurrence of abdominal wall endometrioma without any surgical intervention₁₅.

Scar endometriosis most commonly occurs after operation on the uterus and tubes. The incidence following hysterotomy is 1.08-2% where as after cesarean section the incidence is 0.03-0.4%₅. The reason for higher incidence after hysterotomy has been given as the early decidua has more pleuripotential capabilities and can result in cellular replication producing endometriomas.

Time interval between operation and presentation has varied from 3 months to 10 years in different series₅. In the present case, it was two years.

Scar endometriosis is rare and difficult to diagnose, often misdiagnosed as stitch granuloma, inguinal hernia, lipoma, abscess, cyst₁₆, incisional hernia₁₇, desmoid tumor, sarcoma, lymphoma, or primary and metastatic cancer₂.

A high index of suspicion is recommended when a woman presents with post operative abdominal lump₁₈.

A good surgical and gynaecological history, as well as a thorough examination with appropriate imaging techniques (ultrasound, CT or MRI) will usually lead to a correct diagnosis. The presence of cyclic pain in an incisional mass associated with a cesarean section scar is almost pathognomonic for the condition. Some authors believe that when the diagnosis is made on clinical grounds, no further studies are necessary before wide surgical excision₁₆.

On the contrary, review of the surgical literature indicates that preoperative diagnosis is often incorrect₁₉, ₂₀. Hence, whenever the diagnosis is uncertain, efforts should be made to make a preoperative diagnosis with the help of imaging techniques and FNAC. FNAC has been reported to be accurate in diagnosis₂₃ but in a recent report by Dwivedi et al ₂₄, this was not diagnostic in any of the four patients who underwent this procedure. Nonetheless it may be helpful in eliminating malignancy from the diagnosis. Caution should be used if suspicion of incisional hernia is present₂₅.

Sonographic and color Doppler when combined with clinical data may substantially contribute to the preoperative diagnosis₂₁. These lesions appear as hypoechoic, vascular, and solid, with some cystic changes. CT usually shows a solid, well-circumscribed mass. MRI can be more helpful when the lesion is small because of its high spatial resolution, furthermore it is better than CT scan in detecting the planes between muscles and abdominal subcutaneous tissue₂₂.

Treatment of choice is always total wide excision of the lesion and may sometimes require mesh placement₂, ₄, ₆, ₈.

Medical treatment with the use of progestogens, oral contraceptive pills, and danazol is not effective and gives only partial relief in symptoms and do not ablate the lesion. Moreover due to side effects such as amenorrhea, weight gain, hirsutism, and acne, compliance is unlikely. Recently there has been report of use of gonadotrophin agonist (Leuprolide acetate) but has been found to provide only prompt improvement in symptoms with no change in the lesion size₂₉.

Malignant change of endometriosis in a cesarean scar (CS) is rare₂₆. Long-standing recurrent scar endometriosis could undergo malignant changes and clinician should be aware. Only 21.3% of cases of malignant transformation of endometriosis occur at extragonadal pelvic sites, 4% of cases in scars after laparotomy₂₇. Clear-cell carcinoma is the most common histological subtype, followed by endometrioid carcinoma₂₈. In the literature, survival rate reaches only 57% after a short follow-up of 20 months. Treatment is radical surgical resection followed by prosthetic abdominal wall repair. Compared with endometriosis-associated ovarian carcinoma, the prognosis of abdominal scar complication is poor₂₈.

These patients need to be followed up because of the chances of recurrence, which require re-excision₁₀. In cases of continual recurrence possibility of malignancy needs to be ruled out.

Good technique and proper care during cesarean section may help in preventing endometriosis. It has been suggested that at the end of surgery especially on uterus and tubes, the abdominal wall wound should be cleaned thoroughly and irrigated vigorously with high jet solution before closure₃₀.