Alveolar soft-part sarcoma. A study of 13 typical examples and one with a histologically atypical component.

Thirteen cases of typical alveolar soft-part sarcoma and one in which the tumor had a histologically atypical component are presented. The atypical zone in the latter case was characterized by increased nuclear hyperchromatism and pleomorphism, increased nuclear-cytoplasmic ratio, decreased cytoplasmic eosinophilia and granularity, a less distinct "nesting" pattern, and more numerous mitotic figures. The tumors occurred almost entirely in the younger decades and involved a variety of soft tissue sites. Sex distribution was 1:1, and there was a slight left-sided predominance in tumor location. Median survival of the patients with typical alveolar soft-part sarcoma was 79 months (the patient with the atypical neoplasm died at 36 months). The major factor related to both survival and the likelihood of metastasis was tumor size.