Lobular Carcinoma of the Breast Metastatic to the Ovary: A Clinicopathologic Study of 38 Cases.

We evaluated the clinicopathologic features of 38 cases of metastatic lobular (n=33) or predominantly lobular (n=5) carcinoma involving the ovary. The patients were from 39 to 91 years of age (mean: 53 y). In 2 cases, the breast primary and ovarian metastasis were diagnosed synchronously, and in 5, the breast primary was only discovered after the metastatic carcinoma in the ovary was found. In the majority of cases (79%), both ovaries were involved; the mean ovarian tumor size was 5.9 cm. The ovarian tumors demonstrated a range of architectural patterns including macronodular (71%), diffuse/solid growth (87%), single-cell infiltration (87%), cords (74%), and small nests/clusters (50%). Nine cases demonstrated focal signet ring cell morphology. The associated stromal reaction ranged from none to marked, with almost half of cases demonstrating a marked stromal response, largely prominent sclerosis. A variety of neoplasms, most typically sex cord-stromal tumors, lymphoma/leukemia, and desmoplastic small round cell tumor, may enter the differential. In addition to the obvious help afforded in most cases by the clinical history, a combination of judicious sampling, particularly to unearth the delicate cords or single-cell growth of lobular carcinoma, appropriate consideration of the cytologic features of the neoplastic cells, and immunohistochemistry can resolve the diverse issues in differential diagnosis that may arise.