Micropapillary serous carcinoma of the ovary: Cytomorphologic characteristics in peritoneal/pelvic washings

BACKGROUND. Micropapillary serous carcinoma (MPSC), a recently described entity, is an ovarian tumor with a distinctive histologic architecture that lacks a destructive infiltrative growth pattern and behaves like a low-grade neoplasm. The purpose of this study was to determine if specific cytomorphologic features were associated with this tumor in peritoneal/pelvic washings. METHODS. Eight cases of MPSC were retrieved from the cytopathology files at The Johns Hopkins Hospital. Patients ranged in age from 31 to 74 years (mean, 58 years). A cytomorphologic comparison was made with pelvic washings of eight cases of papillary serous carcinoma (PSC) of the ovary. RESULTS. MPSC demonstrated small but well formed papillary fragments (generally < 30 cells) composed of monotonous, relatively small epithelial cells, often with multiple nucleoli. Single, large atypical cells were seldom present and were seen in less than one half of cases. Cellularity was generally high and slide background was clear with minimal inflammatory cells. In comparison, PSC, in addition to the smaller papillary fragments, also exhibited larger more complex papillary fragments (generally > 30 cells) composed of pleomorphic, hyperchromatic cells often with single prominent nucleoli. Single, large tumor cells exhibiting eccentric atypical nuclei or multinucleation were present in high concentration in the majority of PSCs. Psammoma bodies were observed in one half of cases in both tumor types. CONCLUSIONS. Although MPSC shares cytomorphologic similarities with PSC, it can be diagnosed adequately in peritoneal/pelvic washings. Careful interpretation of the subtle cytologic differences seen in the two tumor types may facilitate the differentiation of these neoplasms for a more appropriate management of the patient.