Breast Carcinoma: An Unusual Variant

Diagnosis

Pure, Mucinous (Colloid) Carcinoma of the Breast

Fine needle aspiration of this breast carcinoma suggested a diagnosis of mucinous carcinoma. Although fine needle aspiration is an excellent tool for the diagnosis of breast carcinoma, the diagnosis of pure colloid carcinoma must be rendered with caution. Lack of necrosis, low grade nuclei and abundant extracellular mucin are cytologic features that would suggest a pure mucinous carcinoma ² . Therefore the fine needle aspiration findings need to be further correlated with the gross as well as microscopic features of the resected tumor

The typical gross appearance of pure, mucinous (colloid) breast carcinoma is that of a a circumscribed tumor that has a gelatinous, moist, glistening surface. Because this tumor was firm, circumscribed and there was focal necrosis, the possibility of either a mixed mucinous carcinoma or a medullary carcinoma was entertained in spite of the fine needle aspiration features of a colloid carcinoma. The discrepancy between the gross features of the breast carcinoma and the findings on fine needle aspiration cytology that prompted ultrastructural examination of this breast carcinoma.

The reported ultrastructural features of pure, mucinous carcinomas of the breast include tightly packed clusters of neoplastic cells, microvillous cytoplasmic processes, rare intracytoplasmic lumens, extracellular lumens, mucin granules and dense core granules ^{1, 2}. Each of these ultrastructural features, except dense core granules, was present in this tumor. Although a rare signet ring cell was also seen in this case of mucinous breast carcinoma, this finding did not cause a . Large numbers of signet ring cells in pure mucinous carcinomas are uncommon and when this feature is present, then pure mucinous carcinoma must be distinguished from signet ring cell carcinomas and infiltrating lobular breast carcinoma.