[Histopathologic and immunohistochemical study of rhabdomyosarcoma]

Histopathologic and immunohistochemical study of 120 cases of soft tissue malignancy diagnosed as rhabdomyosarcoma is reported. There were 65 males and 55 females including 62 adults (greater than or equal to 15 years) and 58 children (less than 15 years). In the adult group, the tumor was common in the limbs and the trunk, whereas in the children group, the urogenital system and regions in the head and neck. Histologically, they were divided into three types: 1. embryonic type (65 cases), 2. alveolar type (28 cases) and 3. polymorphic type (27 cases). Fifty-two cases of proved rhabdomyosarcoma and 21 cases of misdiagnosed rhabdomyosarcoma were stained immunohistochemically with myoglobin antiserum. Forty seven of those 52 cases were positive to various degrees, whereas all the misdiagnosed cases were negative. It was evident that these doubted cases were misdiagnosed in previous histopathologic interpretation. Our study suggests that the immunohistochemical myoglobin stain be an important method for the differentiation of rhabdomyosarcoma. The cause of histopathologic misdiagnosis and the significance of myoglobin antiserum in the histopathologic diagnosis and differential diagnosis of this tumor are discussed.