Abstract
BackgroundMucosal melanomas are rare and have a high potential for metastasizing. Surgical resection is the treatment of choice for single distant metastases. Malignant melanoma usually shows the highest uptake of fluorine-18 fluorodeoxyglucose (18F-FDG). 18F- FDG positron emission tomography /computed tomography (PET/CT) is usually used for melanoma staging. An extensive literature review revealed only 4 published case reports and an original paper involving 8 cases (12 cases in total) of patients with skin melanomas in whom pigmented villous nodular synovitis (PVNS) mimicked metastatic melanoma, however, none of the melanomas reported were of rectal mucosal origin.Case presentationA 60-year-old woman presented with recent diagnosis of rectal mucosal melanoma, two additional 18F-FDG-avid lesions in the left ankle and left foot were detected on 18F-FDG PET/CT. Metastases were initially suspected; however, the final diagnosis was PVNS.ConclusionsThis is the first report of PVNS mimicking metastases on 18F-FDG PET/CT in a patient with rectal mucosal melanoma. Although high 18F-FDG-avid lesions in patients with rectal mucosal melanoma are highly suspected to be metastasis and warrant an meticulous examination, the present case is a reminder that in such patients, not all lesions with high 18F-FDG uptake, especially those near a joint, are metastases and that more extensive resection is unnecessary.
Highlights
Mucosal melanomas are rare and have a high potential for metastasizing
We describe the case of a patient with rectal mucosal melanoma and two additional 18F-FDG-avid lesions, one in the left ankle and one in the left foot
Because anorectal melanomas have a high metastatic potential and high 18F-FDG uptake, any distant lesion that is highly 18F-FDG-avid is suspected as being a possible metastasis, and for any resectable 18F-FDG-avid lesions that are identified, aggressive surgical management is presumably necessary
Summary
Mucosal melanomas are rare and have a high potential for metastasizing. Surgical resection is the treatment of choice for single distant metastases. We describe the case of a patient with rectal mucosal melanoma and two additional 18F-FDG-avid lesions, one in the left ankle and one in the left foot. These lesions were detected on 18F-FDG PET/CT and initially suspected to be metastases, but the final diagnosis was PVNS.
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