Extragastrointestinal stromal tumors (EGISTs) are relatively rare soft tissue neoplasms arising from the extra gastrointestinal tract. The current study presents a case of primary EGIST of the prostate observed in a 55-year-old male. Imaging studies showed a 10×10.5×9.5-cm prostate mass. On histological observation, the mass was separated from the rectum serosa and exhibited a high mitotic count (8/50 high-power fields). The results of immunohistochemical staining showed positive immunoreactivity for cluster of differentiation (CD)117 (c-kit), CD34 and DOG1 in the tumor. On mutation analysis, loss of heterozygosity of the c-kit gene was observed in the prostatic EGIST; however, the platelet-derived growth factor receptor-α (PDGFRA) gene was considered to be normal. Therefore, as EGIST of the prostate is rare, there is a requirement for the confirmation of the diagnosis to be based on immunohistochemistry and mutation analysis (of c-kit and PDGFRA).
Keywords: c-kit; extragastrointestinal stromal tumors; platelet-derived growth factor receptor-α; prostate.