Primary prostatic extragastrointestinal stromal tumor: a case report and literature review

Abstract

Objective This study was performed to discuss the characteristics, diagnosis, and treatment of primary prostatic extragastrointestinal stromal tumor (EGIST). Methods The case history data of a patient with an EGIST were analyzed and discussed with a literature review. Results The patient was diagnosed with a pelvic tumor, possibly malignant. We ascertained the diagnosis by exploratory surgery and pathological biopsy. The tumor was present in the prostate and infiltrated and pressed against the anterior rectal wall. Pathological biopsy showed that the tumor comprised spindle cells, which were also present at the junction of the tumor and prostate tissue. Immunohistochemically, the tumor cells were positive for CD117, DOG-1, CD34, and smooth muscle actin and negative for S100 and desmin; Ki-67LI was about 10%. These results support the diagnosis of primary prostatic EGIST. Conclusion The rarity and nonspecific clinical manifestation of prostatic EGIST facilitate misdiagnosis. Diagnosis mainly depends on imaging examination and characteristic histopathological and immunohistochemical features, and GIST must be excluded. Surgery is the main treatment method, and imatinib is suggested for unresectable and malignant EGISTs.

Keywords: Extragastrointestinal stromal tumor; clinical manifestation; diagnosis; imatinib; prostate; treatment.

Figure 1.

Pelvic computed tomography. (a) Asymmetrical enlargement of the prostate and uneven cell density. (b) The prostate was asymmetrically enlarged and pressed against the anterior rectal wall.

Figure 2.

Pathological and immunohistochemical observations. (a–c) Biopsy-obtained pathological sections (hematoxylin–eosin; 4×, 20×, 40×). Disordered diffusion of tumor cells, mainly comprising spindle cells, was observed in a braiding shape. (d–f) Immunohistochemical examination of CD34, CD117, and DOG-1 in biopsy specimens. Positive expression of CD117, CD34, and DOG-1 was widespread among the tumor cells.