Mucinous carcinoma of breast: A diagnostic pitfall

Abstract

Mucinous carcinoma is also known as mucoid carcinoma, colloid carcinoma, gelatinous carcinoma and mucin producing carcinoma. They are uncommon neoplasms of the breast and the reported incidence varies from 1–4%. Most of the mucinous carcinomas occur in older age group. FNAC can aid in diagnosis of mucinous carcinoma with only a few FNAC studies documented in literature. We present here a 56 year old lady with a huge ulcerated breast mass clinically diagnosed as Malignant Phyllodes tumor. An FNAC was done which showed epithelial cell clusters with mild atypia in a background of both bluish violet and pink extracellular material. Spindle shaped cells were noted in the ground substance which led to a diagnosis of a phyllodes tumor with extensive myxoid change. Mastectomy was performed and the histopathological features confirmed a diagnosis of mucinous carcinoma. The tumor had areas showing thick collagenized fibrous septae separating tumor cell clusters and also areas of fibrosis. The pitfall in FNAC diagnosis may be due to the sampling from such an area.