case_images: PMC3896964_01
case_images: Findings on colonoscopy and endoanal ultrasound scanning. (a) Colonoscopic examination showed a submucosal tumor 3 cm in diameter arising in the posterior rectal wall. (b) Endoanal ultrasound scanning showed a heterogeneous, low-echoic tumor with a nodular appearance arising in the muscularis (long arrow) of the posterior rectal wall.
case_images: 1477-7819-12-12-1.jpg
case_images: PMC3896964_01_1477-7819-12-12-1.jpg
case_images: F1
case_images: Colonoscopic examination in our hospital revealed a submucosal tumor 3 cm in diameter arising in the posterior rectal wall, 10 cm from the anal verge (Figure 1a). An endoanal ultrasound scan showed a heterogenous, low echoic, nodular tumor arising in the muscularis of the posterior rectal wall (Figure 1b).
case_images: Appearance of tumor stained with hematoxylin and eosin. The tumor consisted of round and polygonal cells with clear-to-eosinophilic granular cytoplasm. The tumor cells proliferated in a honeycomb-like fashion.
case_images: 1477-7819-12-12-2.jpg
case_images: PMC3896964_01_1477-7819-12-12-2.jpg
case_images: F2
case_images: The tumor cells proliferated in a honeycomb-like appearance (Figure 2).
case_images: Immunohistochemical findings of the tumor. (a) HMB-45 is positive in the cytoplasm of the tumor cells. (b) Nuclear expression of TFE3 is observed in the tumor cells. HMB-45, melanoma-associated antigen; TFE3, transcription factor E3.
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case_images: PMC3896964_01_1477-7819-12-12-3.jpg
case_images: F3
case_images: Immunohistochemically, the tumor cells were positive for melanoma-associated antigen (HMB-45), neuron-specific enolase, CD68, and transcription factor E3 (TFE-3), but negative for AE1/AE3, CAM5.2, epithelial membrane antigen, smooth muscle actin, Desmin, MyoD1, Caldesmon, Calponin, Synaptophysin, Chromogranin A, NCAM, Vimetin, CD34, S-100, Melan-A, CD99, CD10, D2-40, CD138, P-ALP, and multiple myeloma oncogene-1 (Figure 3ab).