Pure and mixed mucinous carcinoma of the breast: fine needle aspiration cytology findings and review of the literature

Abstract

Mucinous (colloid) breast carcinoma accounts for 1-6% of all breast cancer. It comprises pure mucinous tumours and mixed infiltrating ductal carcinomas with a mucinous component. As this latter mixed form has a worse prognosis than pure colloid carcinoma, making this diagnosis on fine needle aspiration cytology (FNAC) might influence the choice of treatment. We report a consecutive series of 22 cases consisting of 17 mixed and five pure mucinous carcinomas diagnosed by cytology and verified on histopathology. Patients underwent FNAC at the one-stop clinic of our institution during a 7-year period of time. Cytological findings were evaluated by a semi-quantitative method and included percentage of smear surface occupied by mucin, shape of cell groupings, size and outline of tumour nuclei as well as presence or absence of nucleolus. Three of five pure mucinous carcinomas displayed at least two of the following features: abundant mucin, small nuclei and/or regular nuclear outlines. Sparse mucin, large nuclei, irregular nuclear outlines or the presence of nucleoli were found in 7 out of 17 mixed mucinous carcinomas but not in pure tumours. Cytopathological identification of patients with pure mucinous carcinomas may be performed in a limited number of cases.