Metaplastic breast carcinoma on fine-needle cytology samples: a report of three cases

Metaplastic breast carcinoma (MBC) may have a varied presentation on fine-needle cytology samples. We herewith describe three cases of MBC found in our series. One of these cases showed a peculiar mixture of malignant ductal, apocrine type, and squamous epithelial cells with fascicles of spindle cells with variable degree of atypia and was diagnosed as metaplastic carcinoma of the carcino-sarcomatous type. The other two lesions were characterized by an abundant chondroid extracellular matrix to which were variably admixed carcinomatous and chondroid-type cells, with variable degree of atypia. Both these latter cases were defined as matrix-producing metaplastic carcinomas. Because of the various presentation of MBC on fine-needle cytology samples and the possible influence of needle "sampling" on the cytological specimen, the spectrum of differential diagnoses to be considered may encompass a number of benign and malignant entities, like keratinous subareolar cysts, malignant fibroepithelial lesions with myxo-chondroid stroma, and true sarcomas of the breast, with cartilaginous metaplasia. It is the Authors' feeling that, with optimal samples, the cytomorphological findings of this rare variant of breast carcinoma permit its accurate pre-operative diagnosis.