Fig. 2

Hematoxylin–eosin (HE) staining, 200-fold enlargement. Patient 1 Pleomorphic tumor with high cellular density and malignant spindle-shaped, sarcomatoid tumor tissue not clearly indicating one tumor entity. Patient 2 Poorly differentiated, mesenchymal tumor tissue with storiform growth pattern diagnosed as a UPS. Patient 3 Very poorly differentiated malignant cells with high proliferative activity lacking further characteristics that indicate one specific tumor entity. Patient 4 Pleomorphic, mesenchymal tumor tissue with high cellular density suggestive of a previously diagnosed synovial sarcoma. Patient 5 Highly proliferative, pleomorphic and partially spindle-shaped tumor tissue not clearly indicating one diagnosis