Immunohistochemical distribution of basement membrane type IV collagen and laminin in synovial sarcoma.

AIMS

To investigate the distribution of basement membrane components type IV collagen and laminin in synovial sarcomas.

METHODS

Paraffin sections from synovial sarcomas were studied by the peroxidase-antiperoxidase procedure using specific antibodies to type IV collagen and laminin.

RESULTS

Type IV collagen and laminin immunoreactivity was confined around epithelial areas in biphasic tumors. Several interruptions and discontinuities of the linear basement membrane profile were seen in sites of transition between mesenchymal and epithelial tissue. Moreover, a spot-like immunoreactivity was often observed in the spindle cell component of biphasic tumors. Monophasic tumors were either negative or showed a pericellular staining for both type IV collagen and laminin.

CONCLUSIONS

The distribution of basement membrane components is clearly related to the formation of epithelial elements in biphasic synovial sarcoma. The spot-like immunoreactivity of the spindle cell component, and the basement membrane interruptions at the boundary between mesenchymal and epithelial tissue, are both consistent with early basement membrane formation by developing epithelium. These findings support the concept that synovial sarcomas are basically soft tissue carcinosarcomas and that the epithelial component of the tumors develops by conversion of mesenchyme to epithelium.