Although a number of authors have noted aberrant expression of cytokeratins, CD30, CD117 and neuroendocrine markers (synaptophysin and chromogranin A) in AS, intense positive nuclear staining for S100 protein in neoplastic cells has not hitherto been observed.
The PI3K/Akt pathway is activated in both angiosarcoma of bone and soft tissue, however, with a different cause; PTEN expression is decreased in angiosarcoma of bone, whereas angiosarcomas of soft tissue show overexpression of KIT.
KIT positivity has been variably reported in sarcomas such as angiosarcoma, Ewing sarcoma, synovial sarcoma, leiomyosarcoma, and MFH; results of the last three are controversial.
None of the four KIT-positive angiosarcomas and one KIT-positive Kaposi sarcomas that were studied showed mutations in the juxtamembrane or tyrosine kinase domains of the c-kit gene.