PMC6698315_01
Colonoscopy findings demonstrating the manifestation of a pigmented neoplasm at the dentate line.
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Subsequently, colonoscopic examination revealed a pigmented neoplasm measuring 5 mm that had arisen at the dentate line (Fig. 1).
Positron emission tomography-computed tomography findings Accumulation of 18F-fluorodeoxyglucose is visible in a mass at the anorectal junction.
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Tumor biopsy revealed malignant melanoma. 18F-Fluorodeoxyglucose (FDG) positron emission tomography (PET)-computed tomography (CT) revealed tracer accumulation in the mass at the anorectal junction but no evidence of lymph nodes or distant metastases (Fig. 2).
Endoscopy showing transperineal dissection in the caudal-cranial direction.
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TpAPR (equivalent to TaTME) using a multiport device (GelPoint Mini; Applied Medical, Rancho Santa Margarita, CA, USA) (Fig. 3). The laparoscopic transabdominal procedure involved dissection according to TME and high central ligation of the inferior mesenteric artery.
The resected specimen showing invasion of the pigmented tumor to the perirectal tissue at the anorectal junction.
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However, no tumor invasion of the resected margin (Fig. 4), and no lymph node metastases were detected.
Pathological findings.. a) Hematoxylin-eosin staining revealed that atypical cells formed the nests, and spread into the anal canal tissue. b) Enlarged view of tumor cells. Pigmentation was prominent, and the tumor cells had large nucleoli. c, d) Immunohistochemistry showed that tumor cells showed expression of HMB-45 and S100. Original magnification: a: 40x, b-d: 400x.
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Pigmentation was prominent, and the tumor cells had large nucleoli (Fig. 5a, b). Immunohistochemistry showed that tumor cells showed expression of HMB-45 and S100 (Fig. 5c, d).