A clinicopathologic and immunohistochemical study of 16 patients with small intestinal leiomyosarcoma. Limited utility of immunophenotyping.

Abstract

Clinicopathologic data including immunophenotypic expression of 16 new cases of small intestinal leiomyosarcoma are presented. Patient age ranged from 27 to 87 years (mean, 61 years) with a 2.2:1 male-female ratio. Eighty-eight percent of tumors occurred distally, i.e., in the jejunoileum. Considerable histologic heterogeneity was noted including epithelioid, myxoid, and sclerotic variants. Stratification by histologic grade suggests important clinical subsets. Only in grade I tumors is surgical extirpation alone potentially curative. Grade II tumors are associated with meaningful survival usually measured in years, however, nearly all patients can be expected to die from their tumors. Grade III sarcomas are fully malignant and rapidly progressive: except for one case with limited follow-up, all patients with Grade III sarcomas died of disease with a mean survival of only nine months (median, 2 months). Immunostaining with antibodies directed against vimentin, muscle-specific actin, desmin, and S-100 protein were performed. Only antivimentin was uniformly reactive. Sixty-three percent of cases tested showed actin immunoreactivity, and no tumors revealed immunohistochemically detectable desmin or S-100 protein. Although many small bowel stromal sarcomas appear "poorly differentiated" by immunohistochemical methods presently available, that they are indeed leiomyosarcomas seems most likely from their intramural location and light histologic study. The limited utility of immunophenotyping and the importance of histologic grading are stressed.