Fig. 1

a Metaplastic breast squamous cell carcinoma shows nests of malignant squamous cells with keratin pearls formation (hematoxylin and eosin, original magnification × 400). b Metaplastic breast carcinoma shows groups of malignant cells with chondroid and myxoid background (chondroid differentiation) (hematoxylin and eosin, original magnification × 200). c Metaplastic breast carcinoma shows sheets of malignant cells with areas of osteoid-like material (osseous differentiation) (hematoxylin and eosin, original magnification × 200). d Metaplastic breast spindle cell carcinoma shows spindle cell morphology of the tumor cells (hematoxylin and eosin, original magnification ×400). e Metaplastic breast carcinoma shows positive reaction to cytokeratin in the epitheloid and the spindle cells (cytokeratin immunostaining, original magnification ×400)