In a reproductive‑age woman with a painful cyclic nodule at a prior cesarean‑section scar, is scar endometriosis malignant?

Is Scar Endometriosis Malignant?

Scar endometriosis is benign, not malignant. This condition represents ectopic endometrial tissue implanted in a cesarean section scar that responds to hormonal stimulation but does not undergo malignant transformation in the vast majority of cases 1, 2.

Key Diagnostic Features That Confirm Benign Nature

Cytological and histopathological examination consistently demonstrates benign characteristics:

• Fine needle aspiration cytology (FNAC) shows epithelial clusters, fusiform stromal cells, and numerous hemosiderin-laden macrophages—features of benign endometrial tissue, not malignancy 3
• Mild to moderate epithelial atypia may be observed in some cases, but this represents reactive changes rather than malignant transformation 3
• Histopathological examination after surgical excision confirms the diagnosis of endometriosis without evidence of carcinoma 1, 2

Clinical Presentation That Distinguishes It From Malignancy

The cyclic nature of symptoms is pathognomonic for benign scar endometriosis:

• Patients present with intermittent, cyclical pain and swelling at the cesarean scar site that fluctuates with the menstrual cycle 1, 4
• The nodule may increase in size cyclically, corresponding to hormonal changes 4
• Symptoms typically appear 3-8 years after cesarean section, with an incidence of only 0.03-0.4% post-cesarean 2, 3, 4

Important Diagnostic Caveat

While scar endometriosis mimics carcinoma clinically, imaging and cytology reliably exclude malignancy:

• The diagnostic challenge lies in the clinical presentation of a painful abdominal wall mass, which can raise concern for malignancy 1
• FNAC provides a safe and effective tool to differentiate endometriosis from benign or malignant masses, obviating the need for more invasive procedures 3
• Imaging studies reveal characteristic nodular lesions, and FNAC confirms the diagnosis while ruling out malignancy 1

Definitive Management

Wide surgical excision with 1 cm histologically proven free margins is the treatment of choice:

• Complete excision prevents local recurrence, which occurs when margins are inadequate 2
• Surgery results in resolution of symptoms with no recurrence during follow-up when margins are adequate 1, 2
• Consider exploratory laparoscopy in symptomatic patients to exclude intraperitoneal spread, as scar endometriosis may be associated with pelvic endometriosis 2

Risk of Malignant Transformation

Malignant transformation of scar endometriosis is exceedingly rare and not a primary clinical concern:

• While endometriotic nodules theoretically need evaluation for possible malignant transformation, this is extraordinarily uncommon 3
• The literature does not support routine concern for malignancy in typical scar endometriosis cases 1, 2, 3, 4, 5