Necrosis in 84 ovarian carcinomas: a morphologic study of primary versus metastatic colonic carcinoma with a selective immunohistochemical analysis of cytokeratin subtypes and carcinoembryonic antigen.

Carcinomas metastatic to the ovary are often difficult to distinguish from primary ovarian carcinomas. Adenocarcinoma of the colon may simulate both primary endometrioid and mucinous ovarian tumors. The histologic finding of "dirty" necrosis in association with a "garland" or cribriform pattern has been suggested as a useful feature in distinguishing metastatic colonic carcinomas from primary endometrioid ovarian carcinomas. This study was performed to determine the use of "dirty" necrosis in distinguishing primary ovarian carcinoma from metastatic colonic carcinoma by studying 71 of the former and 10 of the latter. At least focal dirty necrosis was found in 68% of primary ovarian epithelial cancers, including 92% of the endometrioid subtype, and in 100% of the metastatic colonic carcinomas. A subgroup of cases was evaluated immunohistochemically using cytokeratin (CK) 7, CK 20 and carcinoembryonic antigen (CEA). The phenotype of CK 7 +/CK 20-/CEA-was present in 92% of primary ovarian carcinomas studied, whereas, 90% of metastatic colonic carcinomas were CK 7-/CK 20 +/CEA+. The finding of dirty necrosis is not specific for metastatic colonic cancer, and differential cytokeratin immunostaining is a useful adjunct in this differential diagnosis.