Neoplasms that occur as primary tumors outside the alimentary tract, and that exhibit similar morphological, immunophenotypical and molecular genetic characteristics to GISTs, are known as EGISTs. Due to the EGISTs, it is important to confirm whether the tumor is associated with the digestive tract, prior to making the diagnosis of EGIST. There are few case reports concerning EGISTs with a potential origin in the prostate; however, several cases of GISTs arising from the rectum have been misdiagnosed as prostatic EGISTs (5
). When making a diagnosis of prostatic EGIST, it is necessary for clinicians to be prudent. The first case of a GIST that potentially originated from the prostate was revealed by Van der Aa et al
). A 49-year-old male was demonstrated to have a large prostatic mass, and a biopsy revealed the presence of a GIST. Treatment with imatinib resulted in a reduction in the size of the mass. However, it was not possible to confirm the diagnosis of prostatic EGIST in the absence of surgical excision. In the present case, enteroscopy and CT revealed no abnormalities intra- or extrarectally, and the light microscopy examination and immunohistochemical analysis of the biopsy specimens confirmed the pathological diagnosis of GIST. Intraoperatively, the tumor was noted to be confined to the prostate, without involvement of the rectum. The preoperative examinations, pathological results and intraoperative investigations confirmed that the tumor was an EGIST, primarily originating from the prostate. Two additional cases of GISTs of a prostatic origin have been studied by Lee et al
and Yinghao et al
). The patients concerned in these cases received radical prostatectomy, which revealed that the tumors were confined to the prostate.
Surgical resection is currently the primary treatment option for non-metastatic EGISTs (6
). For prostatic masses, transrectal ultrasound-guided prostate biopsies may assist in the determination of a treatment strategy. With regard to prostatic EGISTs, radical prostatectomy is considered to provide satisfactory results. In the present case report, a radical prostatectomy was conducted on the patient, since preoperative examinations did not reveal metastases. Imatinib, a selective protein tyrosine kinase inhibitor, has been demonstrated to be an effective treatment for GISTs and EGISTs (7
). In the present case, the postoperative pathological examination revealed a positive microscopic margin in the surgical specimen. As a result of this, the patient was considered to be at a high risk of recurrence; therefore, the patient received imatinib treatment for 1 year, in addition to surgery. In the two cases of prostatic EGISTs mentioned previously, the patients received surgical treatment without imatinib therapy, since positive microscopic margins were not identified. However, in the present case, the absence of recurrence or metastasis in the 24-month follow-up period indicated that surgery combined with imatinib therapy was an effective course of treatment for this patient.
In conclusion, this study presents a rare case of an EGIST originating from the prostate, which was treated using multi-modal therapy. The results from this case indicate that surgical resection, followed by imatinib therapy, may offer a promising outcome for patients diagnosed with prostatic EGIST, where there is a high risk of recurrence.