Antibodies to epithelial markers, such as cytokeratin (especially low-molecular-weight cytokeratin
CAM 5.2) and EMA, typically stain RCC but not HAB.
Cytokeratin 20 (CK20), a low-molecular-weight cytokeratin
, is specifically expressed in the superficial and in some of the intermediate cells of the normal urothelium. Cytokeratin 20 is detected in some urothelial carcinomas and is associated with recurrence in the bladder. Cytokeratin 7 (CK7) is another intermediate filament that is found in urothelial neoplasia of the urinary bladder.
However, most of the tumor cells, unlike SFT, are positive for high- and low-molecular-weight cytokeratin
. The cells in the monophasic synovial sarcoma are spindle shaped.
The excised tumor tissue was fixed in 10% buffered formalin, processed for paraffin sectioning, and stained with hematoxylin-eosin and immunoperoxidase stains for glial fibrillary acidic protein, neurofilament protein, synaptophysin, low-molecular-weight cytokeratin
, and desmin.
Sarcomatous mesothelioma typically is immunoreactive with low-molecular-weight cytokeratin
, whereas most sarcomas either do not express cytokeratin or do so only focally. Other soft tissue tumors, such as synovial sarcoma, fibrosarcoma, malignant fibrous histiocytoma, and malignant or benign peripheral nerve sheath tumors, can be excluded by their histologic appearance and immunophenotypes.