Cytopathological features of scar endometriosis mimicking an adenocarcinoma: A diagnostic pitfall

Scar endometriosis can be a diagnostic challenge in fine-needle aspiration cytology (FNAC) smears that at times, is the first diagnostic modality in such cases. The challenge is amplified when the clinical details are limited and cytopathological features reveal nuclear atypia. A 33-year-old lady presented with an abdominal swelling that she noticed after she met with a scald. Clinically, the swelling was located lateral to her 3-year-old pfannenstiel incision scar. The initial diagnosis on FNAC was metastatic adenocarcinoma. On review, smears were hypercellular, comprising epithelial cells in groups and focally, regular glandular arrangements, imperceptibly admixed with numerous, relatively smaller, short spindly cells. Epithelial cells exhibited mild to focally, moderate nuclear enlargement/atypia. Subsequent biopsy and excision revealed endometrial glands exhibiting focal nuclear atypia with adjacent stroma. Diagnosis of endometriosis was offered. The results were reinforced with positive estrogen receptor staining in the glands and stroma, along with CD10 positivity in the stroma. The patient was recommended gonadotropin releasing hormone analogs and is presently free of disease a year after her diagnosis. FNAC can be a pitfall in the diagnosis of endometriosis. Correct diagnosis has significant therapeutic implications. Although presence of atypia in such cases should not delude the diagnosing cytopathologist for consideration of endometriosis, it should be documented. The value of clinical history in such cases cannot be overemphasized.