[An immunohistochemical study of myoglobin and S-100 protein in rhabdomyosarcoma]

Twenty seven cases of rhabdomyosarcoma from pathologic files of the Hokkaido University Hospital from 1975 to 1985 were reviewed and the presence of myoglobin and S-100 protein was investigated immunohistochemically. Their average age at diagnosis was 30.7 years (ranging from two months to 77 years) and there was a predilection for males in a ratio of 1.7:1. The common locations were the head and neck. Nine cases were positively stained for myoglobin, mainly in the cytoplasm of rhabdomyoblasts and 19 cases were positive for S-100 protein and alpha-subunit of S-100 protein in the cytoplasm of immature tumor cells as well as of rhabdomyoblasts. In seven cases, both of myoglobin and S-100 protein were demonstrated. Although S-100 protein is not strictly specific, however, these results suggest that the immunohistochemical demonstration of S-100 protein can be a useful diagnostic tool of rhabdomyosarcoma.