Pleomorphic sarcoma as a mimicker of sarcomatous carcinoma

The fourth case of a poorly differentiated sarcoma histologically mimicking a sarcomatous carcinoma is reported. The tumor was focally weakly positive for keratin, moderately focally positive for epithelial membrane antigen, muscle-specific actin, smooth muscle actin, and calponin, and strongly diffusely positive for vimentin. The neoplastic cells were closely apposed, often without intervening intercellular matrix; the cell membranes were straight and contained desmosome-like junctions. The cytoplasm contained a moderate number of mitochondria, rough endoplasmic reticulum, ribosomes, and many vesicles. The karyotype was complex and many chromosomal rearrangements were present. The diagnostic term carcinomatoid sarcoma is proposed for these interesting, insufficiently studies, tumors.