Fine-needle aspiration cytology of endometriosis.

Endometriosis commonly involves the pelvis, but may also present as a palpable mass in extrapelvic sites, such as the abdominal wall or inguinal region, where it can be evaluated by fine needle aspiration (FNA). In this report, we illustrate the findings seen in seven cases of endometriosis diagnosed by FNA in patients with a chief complaint of pain associated with an abdominal wall or pelvic mass, occurring in a setting of prior pelvic surgery. The most common previous surgery was Cesarean section (n = 6), followed by hysterectomy (n = 2), and hernia repair (n = 1). In all cases, cytologic examination revealed a glandular component composed largely of orderly fragments of cohesive epithelial cells, a spindle cell stromal component presenting either as loosely organized tissue fragments or single cells, and rare hemosiderin-laden macrophages. Four cases showed focal cytologic atypia in the glandular component with extreme nuclear atypia identified in two of these cases. Atypical features included nuclear crowding and disorganization, nuclear enlargement, hyperchromasia with irregular chromatin distribution and anisonucleosis, raising the possibility of a coexistent malignancy and recommendation for excision. Although malignancy was not identified in follow-up surgical excision specimens, the wide range of cytomorphologic changes that can be seen in FNA specimens of endometriosis should be recognized. Diagn. Cytopathol. 2017;45:359-363. © 2016 Wiley Periodicals, Inc.