Human mucinous breast carcinomas and their lymph node metastases. A histological review of 247 cases.

In a histologic reevaluation of 247 primary human mucinous breast carcinomas, 207 tumors fullfilled the criteria for further histopathological evaluation. The criteria for entrance in this survey are that at least 25% of the tumor consists of areas of extracellular mucin with small islands of solid epithelial tumor tissue floating in the mucin, and that the extracellular mucin should comprise at least 33% of the total tumor volume. The 247 carcinomas that have been further evaluated have been subclassified into two groups: "pure" mucinous breast carcinomas that consist solely of tumor tissue with extracellular mucin production (95 tumors), and "mixed" mucinous carcinomas that also contain infiltrating carcinoma without extracellular mucin (112 tumor). A significantly greater number of mixed carcinomas than pure carcinomas have an aggressive growth pattern--as defined by tumor size, adherence to overlying skin/bottom fascie, and primary axillary lymph node metastases. The histogenesis of the mucinous carcinomas is briefly discussed in relation to the present observations and the literature. The importance of clearly distinguishing between the mixed and the pure mucinous carcinomas in the diagnosis of these tumors is emphasized.