Immunohistochemical evaluation of dystrophin expression in small round cell tumors of childhood.

Dystrophin, the protein product of the Duchenne muscular dystrophy locus, is a major component of the subsarcolemmal cytoskeleton in skeletal muscle cells and is a relatively muscle specific protein. We evaluated, retrospectively, the expression of dystrophin in 23 small round cell tumors of childhood including: 9 rhabdomyosarcomas, 4 neuroblastomas, 1 ganglioneuroblastoma, 2 small noncleaved cell lymphomas, 1 lymphoblastic lymphoma, 2 medulloblastomas, 2 primitive neuroectodermal tumors, 1 Wilms' tumor, and 1 undifferentiated sarcoma. Frozen sections were stained by the avidin biotin immunoperoxidase technique using a commercially available monoclonal antibody NCL-DYS1 (Novocastra) that recognizes the mid-rod domain (between amino acids 1181 and 1388) of human dystrophin. Positive controls were represented by frozen sections of normal skeletal muscle. Negative controls consisted of substituting the dystrophin antibody for normal rabbit serum. Eight of nine rhabdomyosarcomas revealed positivity whereas, none of the other tumors stained for dystrophin. This study provides evidence that monoclonal antibodies to dystrophin may be a potential useful addition to the panel of muscle markers used to diagnose small round cell tumors of childhood.