Histological diagnosis and grading of soft-tissue sarcomas

Grading methodology for soft-tissue tumors is not yet unequivocally established. The authors use a system that is an elaboration upon that of the National Cancer Institute: grade 1 or low-grade lesions are malignant lesions with minimal risk of metastases with a tendency for local recurrence if not totally excised, and with a capability for progression to a higher grade with recurrence; grades 2 and 3 are high-grade lesions with a significant risk of metastases; grade 2 are lesions with intermediate aggressiveness, and grade 3 are highly malignant lesions with dissemination early in the course of the disease. Whereas the great majority of grade 3 lesions recur within 24 months of the initial diagnosis, patients with grade 2 lesions may go recurrence-free beyond 36 months. Although more experience is needed in grading soft-tissue sarcomas, it is hoped that grading will continue to contribute to the management of patients with malignant tumors of the soft tissue. It represents an adjunct to histological typing, which is useful in conveying the degree of biological aggressiveness as judged by histological features. Histologically 80% of the lesions can be classified on the basis of hematoxylin and eosin-stained sections and other conventional special stains. In some instances electron microscopy and immunohistochemistry are necessary for histotyping. The most challenging area for histopathological differential diagnosis remains the distinction of tumor-like reactive conditions, and pleomorphic benign tumors from sarcomas.