sarcoma epithelioidesA pre-immunohistochemistry term for an appearance by light microscopy which had features of both a mesenchymal and epithelial malignancy. Any tumour so labelled would be viewed with suspicion by current pathologists and would have represented
(1) A purely epithelial malignancy (e.g., spindle cell carcinoma, which also has morphologic features of a mesenchymal malignancy);
(2) A purely mesenchymal malignancy (e.g., epithelioid sarcoma (see there), which also has morphologic features of epithelial malignancy); or
(3) A true mixed tumour (e.g., carcinosarcoma, which has morphologic changes in keeping with both an epithelial and a mesenchymal malignancy).
Differentiation amongst the three requires immunohistochemistry.