Retroperitoneal leiomyosarcomas unassociated with the gastrointestinal tract: a clinicopathologic analysis of 17 cases.

Data are limited on leiomyosarcomas within the abdomen and retroperitoneum, particularly if one discounts those associated with the gastrointestinal (GI) tract. Recently, some authors proposed that certain tumors in this location are more appropriately termed extra-GI stromal tumors, given their histologic resemblance to GI stromal tumors as opposed to conventional soft tissue leiomyosarcomas. We evaluated the clinical and pathologic features of 17 cases of leiomyosarcoma (16 retroperitoneal, one intra-abdominal) and recorded the tumor size, predominant cell type, tumor cellularity, nuclear pleomorphism, extent of tumor cell necrosis, and number of mitotic figures per 10 high power fields (MFs/10HPFs). Cases were only included for study if the excised tumor did not arise from abdominal or pelvic viscera or major blood vessels, if adequate clinical follow-up was available, and if the tumor unequivocally resembled conventional soft tissue leiomyosarcoma, both by light microscopic and immunohistochemical examination. The cohort included 16 women and 1 man, and ages ranged from 44 to 72 years (median, 60 yr). Tumors ranged in size from 6.5 to 29.5 cm (median, 13.5 cm). Fifteen tumors were composed predominantly of spindled cells, one tumor was composed predominantly of epithelioid cells, and one tumor was composed of an admixture of spindled and epithelioid cells. Follow-up intervals ranged from 4 to 169 months (median, 47 mo). Fifteen (88%) of seventeen patients developed an adverse outcome, defined as the development of metastatic disease or death due to tumor. Patients whose tumors had greater than 10 MFs/10HPFs had significantly shorter intervals to either metastasis or death than did those whose tumors had 10 or fewer MFs/10HPFs (8.4 mo vs. 42 mo; P = .003). No other features correlated with time to adverse outcome. In conclusion, the majority of patients with leiomyosarcomas located within the abdomen or retroperitoneum progress to metastatic disease or die from their tumor. The only feature that is significantly associated with a shorter interval to either metastasis or death is more than 10 MFs/10HPFs.