Epidemiology of soft-tissue sarcoma in the locomotor system. A retrospective population-based study of the inter-relationships between clinical and morphologic variables.

From all soft-tissue malignancies reported to the Swedish National Cancer Registry in Southern Sweden (1.3 mill. inhabitants) from 1964 through 1978, 278 cases were accepted as sarcomas after histologic re-examination. All these were malignancy-graded on a four-grade scale, without knowledge of the clinical course. A number of clinical and morphological variables were recorded and subjected to uni-, bi- and multi-variate analysis. Follow-up was available in all patients. The annual incidence rate over all ages was 1.4/100,000. The mean age was 58 years and males dominated (1.3/1). Malignant fibrous histiocytoma, liposarcoma and leiomyosarcoma were the most common histologic groups. Three-fourths of the tumors were high-grade malignant (Grade III-IV). Sixty per cent were deep-seated, having a median size of 8 cm compared to 4 cm for the superficial tumors. One third of all tumors were located in the thigh. The histologic groups were characterized by age, tumor depth and size, the occurrence of pain, malignancy grade and five-year survival; it was seen that each group, with respect to at least one of the variables, differed significantly from all the other groups. Thus histologic classification seems to identify different tumor entities. Out of several pair-wise associations the strongest were as follows: histologic groups versus depth, size, malignancy grade and age; depth versus size; and size versus malignancy grade (Grade IV tumors being larger). The proportion of superficial and small tumors in this series is high, compared to several reported series, probably owing to "referral selection" in the previous studies. The inter-relationships found between several variables and conclusions based on selected series may explain, in part, the differing opinions which can be found in the literature regarding prognostic variables in soft-tissue sarcoma.