Objective: The purpose of this study was to determine the specific diagnoses, relative prevalence, and the age, sex, and skeletal distribution of benign 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.
Materials and methods: The computer diagnoses of 39,179 lesions occurring in 38,484 patients seen by the Armed Forces Institute of Pathology soft-tissue pathologists during the 10-year period starting January 1, 1980, and ending 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, and forearm. Age and sex of the patients were also 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 18,677 were benign.
Results: Approximately two thirds of soft-tissue tumors were classified into seven diagnostic categories: lipoma and lipoma variants (16%), fibrous histiocytoma (13%), nodular fascilitis (11%), hemangioma (8%), fibromatosis (7%), neurofibroma (5%), and schwannoma (5%). Approximately 80% of all benign tumors were placed in seven diagnostic categories for each age and location. In the retroperitoneum, for example, approximately half the benign lesions in the 16- to 25-year old group were fibromatosis (20%), schwannoma (14%), and neurofibroma (13%). For the same location in children 5 years old or younger, almost two thirds of the benign tumors were lipoblastoma (37%) or lymphangioma (26%).
Conclusion: Despite the large number of pathologic possibilities, most benign soft-tissue tumors are classified into a small number of specific diagnostic categories. 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 the radiologist in establishing a suitably ordered differential diagnosis when a soft-tissue tumor has a nonspecific radiologic appearance.