Signet ring carcinoma of the female breast: a clinicopathologic analysis of 24 cases.

Signet ring carcinomas of the breast have been separated recently as an aggressive subtype of breast cancer, distinct from mucinous (colloid) carcinomas. Twenty-four cases of signet ring breast cancer (2% of total breast cancers at the authors' institution) were analyzed. The authors' study indicates that histogenetically such lesions are derived from lobular, not ductal, cells since mucin patterns and ultrastructural features are shared. In addition, in each of our 24 cases, infiltrating lobular carcinoma was identified; in 11 of these (46%) lobular carcinoma in-situ (LCIS) was also noted. Signet ring carcinomas show an unusual metastatic pattern with a propensity to involve serosal surfaces and mimicking gastrointestinal disease or retroperitoneal fibrosis. These tumors are associated with a poor prognosis, with 60% of our 24 patients dead of disease at 7 years. The distinctive clinical and pathologic features of signet ring carcinoma warrant separation of this group of tumors from other forms of breast cancer.