The purpose of this study was to determine the relative prevalence, age at presentation, sex distribution, and skeletal distribution of malignant soft-tissue tumors and to ascertain the relative frequency of these tumors in specific anatomic locations and age groups among a population of patients in a large pathologic consultation service.

The computer diagnoses of 39,179 lesions occurring in 38,484 patients seen by soft-tissue pathologists at the Armed Forces Institute of Pathology during the 10-year period from January 1, 1980, to December 31, 1989, were retrospectively reviewed. All lesions were placed in one of 121 major categories in accordance with the classification system used by the World Health Organization and coded to one of 32 anatomic locations, such as hand, wrist, forearm, and so forth. Age and sex also were recorded. For purposes of analysis, all lesions were placed in one of 10 categories: hand and wrist, upper extremity, proximal limb girdle (axilla and shoulder), foot and ankle, lower extremity, hip and buttocks region, head and neck, trunk, retroperitoneum, and other lesions. The study group included 31,047 mesenchymal lesions, of which 12,370 were malignant.

More than 80% of malignant tumors were classified into eight diagnostic categories: malignant fibrous histiocytoma (24%), liposarcoma (14%), leiomyosarcoma (8%), malignant schwannoma (6%), dermatofibrosarcoma protuberans (6%), synovial sarcoma (5%), fibrosarcoma (5%), and sarcoma, not classified further (12%). Approximately 79% of all malignant tumors were classified into five diagnoses for each age and location. With the distal upper extremity (hand and wrist) as an example, 50% of malignant lesions in the 16-25-year-old group were classified as epithelioid sarcoma (29%), malignant fibrous histiocytoma (13%), and synovial sarcoma (8%). For the same location but for children 5 years old or younger, almost 50% of malignant tumors were classified as infantile fibrosarcoma.

Despite the multitude of pathologic possibilities, most malignant soft-tissue tumors are classified into a small number of diagnoses. These may be further defined when the location of the lesion and the age of the patient are considered. Knowledge of tumor prevalence will assist radiologists in establishing a suitably ordered differential diagnosis when a soft-tissue tumor has a nonspecific radiologic appearance.