PMC4275951_01
(A) Colonoscopy disclosed a SMT in the rectum. (B) Transrectal US demonstrated a hypoechoic mass 18 mm x 18 mm in diameter originating from the submucosal layer (arrow) in the rectum.
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SMT of the rectum. She had no complaints, and the tumor was discovered incidentally as a SMT in the posterolateral wall of the rectum, 10 cm from the anal verge (Fig. 1A) when she underwent colonoscopy for positive fecal occult blood tests on a periodic health checkup. Endoscopic ultrasound (EUS) showed an 18 mm x 18 mm hypoechoic mass (Fig. 1B), and EUS-guided biopsy was performed for immunohistochemical analysis, which revealed weakly positive staining for CD117.
Magnetic resonance imaging. (A) Transverse T1-weighted image demonstrated a homogeneous mass without signal intensity (arrow). (B) Transverse T2-weighted image demonstrated a heterogeneous mass with high signal intensity (arrow).
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T1-weighted and rather hyperintense on T2-weighted images (Fig. 2). The serum levels of carcinoembryonic antigen (CEA) and CA19-9 were within normal ranges.
(A) An intraoperative photograph of transanal endoscopic microsurgery (TEM). (B) Macroscopic view of the resected rectal SMT.
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After discussing the operative procedures and obtaining written informed consent, we attempted local excision of the tumor using transanal endoscopic microsurgery (TEM) (Fig. 3A). The cut surface was uniformly elastic, soft and exhibited bright appearance (Fig. 3B).
Microscopic images. (A) Clusters and palisading of spindle-shaped vesicular-nucleated tumor cells are seen (H-E stain, x200). (B) and (C) Negative immunoreactivity in the tumor cells for CD117 (B, x200) and CD34 (C, x200). (D) Immunohistochemistry indicated strong staining for S-100 (x200). (E) MIB-1 index was 3% (x200).
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Immunohistochemical staining revealed that the tumor cells were positive S-100 and negative for CD34 and CD117 (Fig. 4).