PMC4906122_01
Positron emission tomography-computed tomography: Abnormally high accumulation of fluorodeoxyglucose (25.1 SUV max) was found in the anal region.
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Positron emission tomography-computed tomography detected an abnormal accumulation (25.1 SUV max) consistent with a tumor (Fig. 1).
Physical findings: The base of a black pedunculated raised lesion was found slightly distal to the pectinate line.
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When the anus was spread, mottled black changes approximately 1-2 mm in size that were non-contiguous with the main lesion were observed in over half of the circumference of the opening adjacent to the dentate line (Fig. 2).
Biopsy procedure: biopsies were performed on the scattered mottled black changes at the pectinate line level that were separate from the main lesion.
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Additionally, we performed a biopsy of the dentate line tissue containing the mottled black changes that were not contiguous with the main lesion (Fig. 3).
The surgical specimen: black changes were found at the anal canal.
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Intraepithelial basolateral proliferation of large atypical melanocytes with nuclear irregularity was observed within an extensive 7.0 x 2.3-cm area around the previously excised main lesion, which constituted a finding of malignant melanoma despite the absence of evident interstitial infiltration (Fig. 4, Fig. 5).