Histopathology peer review of high-grade soft tissue sarcoma: the Scandinavian Sarcoma Group experience

From 1981 to 1986, a total of 240 patients with a primary soft tissue sarcoma with malignancy grade III or IV were entered into an adjuvant chemotherapy multicenter trial conducted by the Scandinavian Sarcoma Group (SSG). Histopathologic peer review of all the specimens was performed by an expert pathology committee. The most common soft tissue sarcoma after review was malignant fibrous histiocytoma (MFH) (40%), followed by synovial sarcoma (15%), leiomyosarcoma (9%), liposarcoma (8%), and malignant Schwannoma (6%). In 25% of the cases the histologic type of sarcoma was reclassified, and in 40% of the cases the malignancy grade was changed. By survival analyses, the reclassification of malignancy grade seemed to be valid. Also, grading highly malignant soft tissue sarcoma in two grades (III and IV) increased the prognostic information. Of 164 tumors from the centers with the most reported cases (five centers with 25 to 51 tumors each), eight tumors were found to be ineligible for the adjuvant study (5%); of 76 tumors from 13 centers with few tumors (one to 16 tumors per center), 12 tumors were ineligible (16%). We conclude that histologic peer review is important in studies of soft tissue sarcoma.