Case presentation A 51-year-old woman tested positive for fecal occult blood and underwent colonoscopy, followed by laparoscopic rectal amputation. Medical history History of bipolar disorder History of hyperlipidemia Diagnostic tests: Preoperative: Colonoscopy revealed a 30-mm semi-pedunculated tumor in the lower rectum (Rb) and a black protruding lesion extending into the anal canal (Cover image). Intraoperative findings: The tumor invaded the submucosa, and one lymph node metastasis was detected. Postoperative findings: Pathological analysis of tissue specimens revealed peripheral discontinuous melanin deposition . Histopathological findings - Diffuse proliferation of atypical cells (Figure.
1). Figure 1. Diffused proliferation of atypical cells with prominent nuclei of varying sizes accompanied by melanin depositions. (Source: Surgical Case Reports) Immunostaining - Positive…
