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 loca tion are more appropriately termed extra-GI stromal tumors, given their his tologic resemblance to GI stromal tumors as opposed to conventional soft ti ssue leiomyosarcomas. We evaluated the clinical and pathologic features of 17 cases of leiomyosarcoma (16 retroperitoneal, one intra-abdominal) and re corded the tumor size, predominant cell type, tumor cellularity, nuclear pl eomorphism, extent of tumor cell necrosis, and number of mitotic figures pe r 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 b lood vessels, if adequate clinical follow-up was available, and if the tumo r 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), Tu mors ranged in size from 6.5 to 29.5 cm (median, 13.5 cm), Fifteen tumors w ere composed predominantly of spindled cells, one tumor was composed predom inantly of epithelioid cells, and one tumor was composed of an admixture of spindled and epithelioid cells. Follow-up intervals ranged from 4 to 169 m onths (median, 47 mo). Fifteen (88%) of seventeen patients developed an adv erse outcome, defined as the development of metastatic disease or death due to tumor. Patients whose tumors had greater than 10 MFs/10HPFs had signifi cantly 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 fe atures correlated with time to adverse outcome. In conclusion, the majority of patients with leiomyosarcomas located within the abdomen or retroperito neum progress to metastatic disease or die from their tumor. The only featu re that is significantly associated with a shorter interval to either metas tasis or death is more than 10 MFs/10HPFs.