EXTRACELLULAR-MATRIX OF SMALL ROUND-CELL TUMORS OF CHILDHOOD - AN IMMUNOHISTOCHEMICAL STUDY OF 67 CASES

Sixty-seven childhood tumors were studied immunohistochemically for th e extracellular matrix elements type IV collagen, laminin, and fibrone ctin. Tumors included Ewing's sarcoma, primitive neuroectodermal tumor , small cell osteosarcoma, neuroblastoma or ganglioneuroblastoma, rhab domyosarcoma, and lymphoma. It was found that small cell osteosarcoma was often positive for fibronectin but not type IV collagen or laminin , a new observation. In the lymphomas, matrix proteins were rarely fou nd. Ewing's sarcoma was variably positive for type IV collagen and lam inin, but fibronectin was absent. Extracellular laminin and fibronecti n were found in one of two cases of primitive neuroectodermal tumor. I n neuroblastoma and ganglioneuroblastoma, the matrix components were r arely found. These results, discrepant with findings in cultured cells , may reflect the altered capacity of tumors to produce these proteins in vitro, which suggests that caution should be exercised in drawing conclusions regarding the nature or histogenesis of tumors from data o btained with cultured tumor cells. Embryonal rhabdomyosarcoma frequent ly contained all matrix elements in the extracellular space and in a d otlike pattern in the cytoplasm; alveolar rhabdomyosarcoma rarely cont ained these proteins and never exhibited the dotlike pattern. The freq uent finding of matrix proteins in embryonal rhabdomyosarcoma but only rarely in alveolar rhabdomyosarcoma and the unique immunostaining pat tern in embryonal rhabdomyosarcoma may prove to be a useful adjunct in the diagnosis of childhood tumors.