Retroperitoneal leiomyosarcoma. A clinicopathologic analysis of 36 cases.

Thirty-six cases of retroperitoneal leiomyosarcoma form the basis for this retrospective clinicopathologic study. This group comprised 24 females (67%) and 12 males (33%), whose ages ranged from 12 to 94 years (median, 60 years.). The clinical presentation, invariably nonspecific, consisted of pain or weight loss, typically associated with a palpable abdominal mass. Of the 30 patients with follow-up data, 23 (77%) died of retroperitoneal leiomyosarcoma. Grossly, the bulky often multinodular tumors, which ranged from 7.5 to 35 cm in maximal dimension (median, 12.8 cm), varied from firm to soft. In addition to the classical microscopic picture of leiomyosarcoma as manifested by interlacing fascicles of slender eosinophilic cells, other less frequently encountered, morphologic variations of malignant smooth-muscle tumors were also observed. Although absolute minimal criteria for a malignant tumor diagnosis could not be established, the findings suggest that a retroperitoneal smooth-muscle tumor that measures at least 7.5 cm in greatest dimension and that has as few as 1 mitosis/10 HPF is capable of metastasis.