Histology Course S IX 17 Department of Pathology, University of Zurich Histology Course

S IX 17 synovial sarcoma, biphasic  HE  
  ICD-10: C38.4; ICD-O: 9043/3  

32-year-old female, with swelling of the soft tissue at the shoulder area, slowly increasing over months. Biopsy.

- Cell-dense tumour tissue consisting of two heterogenous mixed components:
1. densely arranged spindle cells with elongated, dense nuclei and mitotic activity
2. epithelioid cell clusters often with formation of glandular structures with intraluminal secretion
- areas of collagenisation, possibly calcification.

The two mentioned components are the reason for the term biphasic. Immunohistochemically expressed is the spindle cell component Vimentin, occasionally also cytokeratine, predominantly the epithelioid type. So-called monophasic synovial sarcomas are only spindle-cell shaped and more difficult to recognize since they do not always express cytokeratin.