Histogenesis of alveolar soft part sarcoma

Six alveolar soft part sarcomas, two granular cells myoblastomas, one carotid body tumor, and one normal carotid body were compared at the ultrastructural level. Strong similarities were noted between the alveolar soft part sarcoma and paragangliomas of carotid‐body type. Similarities were the basic structural unit composed of chief cells, peripheral spindle cells, boundary laminae, and surrounding vascular spaces arranged in a consistent pattern. Secretory‐like granules resembling those of the carotid body were found in the chief cells of the alveolar soft part sarcomas. Other similarities were the presence of light and dark chief cells, randomly located desmosomes between chief cells, and characteristic hemidesmosomes at the periphery of chief cells. There was no similarity to the granular cell myoblastoma. The complex mesodermal and neural histogenesis of the carotid body is discussed and the hypothesis offered that alveolar soft part sarcoma may arise from displaced paraganglionic mesoderm. It is concluded that a close homology exists between alveolar soft part sarcoma and the paragangliomas of carotid body type, and that the tumors are of related histogenesis.