Diagnosis of soft tissue sarcomas.

Based on a review of 752 cases coded as soft tissue sarcomas, histologic features were analyzed for a differential diagnosis, dividing the sarcomas in the first diagnostic step into purely descriptive groups, regardless of biologic behavior: spindle cell, small cell, pleomorphic and myxoid varieties. The tumor categories mainly discussed in order were fibrosarcoma, leiomyosarcoma, malignant schwannoma, synovial sarcoma, malignant fibrous histiocytoma, embryonal and alveolar rhabdomyosarcoma, malignant neuroepithelioma , extraskeletal Ewing's sarcoma, and myxoid and other types of liposarcoma. The discussion was focused on the problems we were facing often in the histologic diagnosis of these tumors, emphasizing in particular those microscopic features which were helpful in differential diagnosis. Principal clinical features, important for an accurate diagnosis, were added to the histopathologic considerations in each item, together with prognosis of all these Japanese patients, regardless of the stages. Other benign and malignant lesions confused occasionally with the soft tissue sarcomas were also listed. With the aid of electron microscopy and immunohistochemistry, sometimes each differentiating feature can be identified but these methods are not always contributory to a diagnosis. Routine light microscopy with or without standard histochemical techniques remains essential to avoid pitfalls when attempting to diagnose the tumor.