BACKGROUND Mucosal 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 PRESENTATION A 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. CONCLUSIONS This 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.

中文翻译：

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直肠粘膜黑色素瘤患者中模仿18F-FDG PET / CT转移的色素性绒毛状结节性滑膜炎：病例报告。

背景技术粘膜黑色素瘤是罕见的，并且具有很高的转移潜力。手术切除是治疗单发远处转移的一种选择。恶性黑色素瘤通常显示最高的氟18氟脱氧葡萄糖（18F-FDG）摄取。18F-FDG正电子发射断层扫描/计算机断层扫描（PET / CT）通常用于黑色素瘤分期。广泛的文献综述仅揭示了4例已发表的病例报告，原始论文涉及8例（共12例）皮肤黑色素瘤患者，其中色素性球状结节性滑膜炎（PVNS）模仿了转移性黑色素瘤，但是，报告的黑色素瘤均无直肠粘膜起源。病例介绍一名60岁的女性最近被诊断出直肠粘膜黑色素瘤，在18F-FDG PET / CT上还检测到左脚踝和左脚另外两个18F-FDG-avid病变。最初怀疑有转移。然而，最终诊断是PVNS。结论这是PVNS模拟直肠粘膜黑色素瘤患者18F-FDG PET / CT转移的首次报道。尽管高度怀疑直肠粘膜黑色素瘤患者存在高18F-FDG-avid病变并需要进行仔细检查，但本案例提醒我们，并非此类患者中，并非所有18F-FDG摄取率高的病变，尤其是附近关节是转移灶，不需要进行更广泛的切除。结论这是PVNS模拟直肠粘膜黑色素瘤患者18F-FDG PET / CT转移的首次报道。尽管高度怀疑直肠粘膜黑色素瘤患者存在高18F-FDG-avid病变并需要进行仔细检查，但本病例提醒我们，并非此类患者中，并非所有18F-FDG摄取率高的病变，尤其是附近关节是转移灶，不需要进行更广泛的切除。结论这是PVNS模拟直肠粘膜黑色素瘤患者18F-FDG PET / CT转移的首次报道。尽管高度怀疑直肠粘膜黑色素瘤患者存在高18F-FDG-avid病变并需要进行仔细检查，但本病例提醒我们，并非此类患者中，并非所有18F-FDG摄取率高的病变，尤其是附近关节是转移灶，不需要进行更广泛的切除。