HLA CLASS-I AND CLASS-II EXPRESSION IN RHABDOMYOSARCOMAS

The expression of class I and II histocompatibility antigens was studied in 43 specimens of skeletal and in 36 specimens of cardiac muscle. Expression was also analyzed in the tumoral counterpart of striated muscle tissue, in 21 rhabdomyosarcomas (13 embryonic, 2 alveolar and 6 pleomorphic). Normal striated muscle showed very weak HLA class I antigen expression and no class II expression. The rhabdomyosarcomas showed increased class I expression, possibly related to malignant transformation of this type of tissue and with the degree of cellular differentiation. In our series of rhabdomyosarcomas, we observed class II neoexpression only in some HLA class I positive specimens, which was unrelated to the degree of cellular differentiation in these tumors.