PMC4200885_01
Magnetic resonance imaging. (A) Transverse T1-weighted image showing a homogeneous mass with intermediate signal intensity (arrow). (B) Transverse T2-weighted image showing a heterogeneous mass with high signal intensity (arrow). (C) Sagittal T2-weighted image could not show clear delineation between the tumor and the prostate (arrow).
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Magnetic resonance imaging (MRI) showed a mass with a smooth margin, 7 cm x 5 cm in size mainly occupying the anterior wall of the lower rectum (Fig. 1).
(A) Resected specimen showing concurrent rectal GIST and adenocarcinoma of rectum. (B) Rectal GIST without prostatic infiltration. UB: urinary bladder; P: prostate; R: rectum.
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To minimize the risk of tumor spread during the dissection between a large fragile GIST and the prostate in the lower pelvic cavity and to accomplish complete en bloc resection of the two concomitant malignant tumors, total pelvic exenteration (TPE) with ureterocutaneous fistula was selected (Fig. 2).
Microscopic images. (A) Rectal adenocarcinoma (H-E stain, x20). (B) Prostate adenocarcinoma (H-E stain, x10). (C) Rectal GIST (H-E stain, x20). (D and E) Immunohistochemistry indicating strong staining for CD117 (D, x20), and CD-34 (E, x40). (F) MIB-1 index was about 15% (x20).
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Immunohistochemical analysis revealed positive staining for CD117 (c-kit), CD-34 and Vimentin, and negative CAM5.2 (Fig. 3).