Alveolar soft part sarcoma, granular cell tumor, and paraganglioma. An immunohistochemical comparative study.

Five cases of alveolar soft part sarcoma, 5 cases of granular cell tumor, and 6 cases of paraganglioma were investigated immunohistochemically to examine the expression of tissue-specific intermediate filaments (cytokeratin, vimentin, desmin, and glial fibrillary acidic protein (GFAP], actin, myoglobin, and nervous tissue markers (S-100 protein, neuron-specific enolase, and Leu-7). In alveolar soft part sarcomas, some of the tumor cells were positive for desmin, but negative for nervous tissue markers. The tumor cells of granular cell tumors were stained with anti-S-100 protein antibody, but not with anti-neuron-specific enolase antibody. In contrast, the tumor cells of paragangliomas were positive for neuron-specific enolase, but not for S-100 protein except for stellate cells surrounding the tumor cell nests. This immunohistochemical approach was valuable for the differential diagnosis of these three tumors. Furthermore, the complete absence of cytokeratin in all of the tumor cells may be helpful in distinguishing these three tumors from metastatic carcinoma in soft tissue. The histogenesis of alveolar soft part sarcoma is a matter of controversy. The result that besides desmin actin was also demonstrated in some of the tumor cells may support the myogenic origin of this tumor.