Open Access

CASE REPORT

Gastrointestinal stromal tumors presenting as a prostatic mass

Gustavo de la Roza¹, Asghar Naqvi¹, Kimball Clark²

1 Department of Pathology, SUNY-Upstate Medical University, Syracuse, New York, USA
2 Department of Radiology, SUNY-Upstate Medical University, Syracuse, New York, USA
Address correspondence to Dr. Gustavo de la Roza, SUNY-Upstate Medical University, Department of Pathology, WSK 2106, 750 East Adams Street, Syracuse, New York 13210 USA

Canadian Journal of Urology 2009, 16(1), 4502-4506.

Abstract

Gastrointestinal stromal tumors (GISTs) are a rare and heterogeneous group of spindle cell neoplasms that have also been reported outside of gastrointestinal (GI) tract. These tumors are characterized by somatic mutations of c-KIT (CD117), a proto-oncogene that encodes a receptor tyrosine kinase normally expressed in the interstitial cell of Cajal that control the GI smooth muscle peristalsis, and an exquisite sensitivity to the action of the tyrokinase inhibitor imatinib mesylate (STI571; Gleevec). We report two cases of gastrointestinal stromal tumor identifi ed on prostatic biopsies, where a primary prostatic sarcoma was considered in the differential diagnosis. In one of the cases, there was extensive local disease involving prostate, rectum, and pelvic wall, as well as metastatic disease that quickly lead to the patient’s death despite aggressive treatment with imatinib mesylate and conventional chemotherapy. In the other case, the tumor was mostly confi ned to the rectum but also focally extended into the prostate capsule. The patient underwent resection and was alive without disease 18 months after surgery. In both cases, tissue samples from prostate and the rectum showed a malignant spindle cell neoplasm, which was positive for CD117 (c-kit). Given their unique clinical management, gastrointestinal stromal tumors should be considered in the differential diagnosis of spindle cell lesions on prostatic needle biopsies and CD117 should be added to the immunohistochemical panel in the work-up of such lesions to avoid misinterpreting them as primary prostatic neoplasms.

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