Clinical Information: 71 year old female with mass in left breast. Core biopsy performed.
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Discussion and answer
Diagnosis: metaplastic carcinoma (squamous cell carcinoma with spindle cell
The core biopsies from the breast tissue show a spindle cell proliferation with intervening adipose tissue and presence of occasional uninvolved mammary ducts surrounded by fibroelastosis and spindle cells. There are foci of well differentiated keratinizing squamous components with intervening strands of cells with moderate amount of
cytoplasm and occasional squamous pearls. Elsewhere the cells form a spindle cell pattern with intervening fibrocollagenous tissue containing fibroblastic cells. Focal lymphocytic and plasma cell infiltrate is present. CK5/6 was positive in the spindle and keratinizing components (not shown). This morphology is consistent with a metaplastic carcinoma which is an intimate mixture of squamous and spindle cell components.