Nongynecologic scar endometriosis with late onset during pregnancy

Scar endometriosis is a rare form of cutaneous endometriosis that typically arises years after abdominal or pelvic surgery, most commonly presenting with cyclic pain and nodular lesions on or near surgical scars. We report the case of a 36-year-old pregnant woman who developed a painless, enlarging nodule on a midline abdominal scar, 24 years after an open appendectomy. The lesion appeared during the first trimester of pregnancy and was initially suspected to be a foreign body granuloma. Ultrasonography revealed a subcutaneous hypoechoic mass without signs of infection or encapsulation. Due to the patient’s advanced gestation, a superficial excision was performed under local anesthesia. Histopathologic examination confirmed the diagnosis of scar endometriosis with decidualized stroma, consistent with hormonally active ectopic endometrial tissue. This case is notable for its late onset, absence of typical symptoms, and development during pregnancy, highlighting the diagnostic challenges posed by atypical presentations. Dermatologists should maintain a high index of suspicion for scar endometriosis, especially in women with prior abdominal surgeries, even in the absence of classical features.