PMC9929663_01
Endoscopic findings. (A) EUS image showing a hypoechoic nodule arising from the second layer of rectal wall (7.5 MHz); (B) endoscopic image of polyp; (C) submucosal injection of saline for lifting the polyp; (D) EMR using Band; (E,F) polypectomy site and polyp after resection. EUS, endoscopic ultrasound; EMR, endoscopic mucosal resection.
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Endoscopic ultrasound (EUS) with a radial echoendoscope was performed to reveal a single 0.8 cm x 0.7 cm hypoechoic nodule located at the anorectal junction (Figure 1A-1C). Endoscopic mucosal resection (EMR) was performed using Band EMR technique, the polyp was completely retrieved, and specimen was sent for histopathological evaluation (Figure 1D-1F).
Microscopic findings. (A) Low power view showing submucosal nodule with overlying normal anorectal mucosa (hematoxylin and eosin, x20); (B) high power view showing lymphoid infiltrate with prominent germinal center formation (arrow) and interspersed nests of neoplastic cells (star) (hematoxylin and eosin, x200).
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The overlying squamous and colonic mucosa was unremarkable (Figure 2A,2B).
Immunohistochemical stains. (A-C) Diffuse strong expression of p40, P63, and P16 respectively in the neoplastic cells (x40). (D) Negative CDX2 in the neoplastic cells with positive staining in the overlying normal colonic mucosa (x40).
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Immunohistochemical analysis revealed diffuse tumor positivity for p16, p40, and p63 (Figure 3A-3C) along with variable co-expression of CK7 and epithelial membrane antigen (EMA). The tumor cells were negative for CDX-2 (Figure 3D), CK20, CEA, chromogranin, synaptophysin, p53, SOX-10, and S100.