Histological changes in recurrent soft tissue sarcomas: analysis of 56 patients.

Histological changes in 56 patients with recurrent soft tissue sarcomas (STS) were analysed. The original tumors included 23 malignant fibrous histiocytomas, five liposarcomas, four leiomyosarcomas, four synovial sarcomas, four neurogenic sarcomas, four dermatofibrosarcomas and 12 other assorted tumor types. The histological features of the recurrent tumors which underwent changes included increased cellularity, an increased number of mitotic figures, extension of sclerotic areas and the appearance of a storiform pattern; these were found in 30%, 43%, 41% and 29% of cases, respectively. No case showed a histological change from one subtype to another. A follow-up study revealed increased cellularity and mitotic counts in the recurrent tumors to be signs of an unfavorable prognosis.