Ajit Nimmagadda, Bikkina Prathyusha, Abubacker Zakir Ali, Virupakshappa C B, Rao S Lm Chandrasekhar, Tagore Koyye Ravindranath, Kodandapani Suseela
Department of Nuclear Medicine, Basavatarakam Indo American Cancer Hospital and Research Institute, Hyderabad, Telangana, India.
Department of Head and Neck Oncology, Basavatarakam Indo American Cancer Hospital and Research Institute, Hyderabad, Telangana, India.
Indian J Nucl Med. 2025 Jan-Feb;40(1):32-35. doi: 10.4103/ijnm.ijnm_123_24. Epub 2025 May 16.
Mucosal melanomas (MMs) represent a rare subset of melanomas arising from melanocytes in noncutaneous sites such as mucosal membranes of the head-and-neck, gastrointestinal, and genitourinary tracts. Unlike cutaneous melanomas, MMs often present late due to their occult nature, leading to a poor prognosis. Fluorine-18 fludeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is widely utilized for staging and monitoring melanomas, leveraging their characteristic high FDG avidity. Recently, fibroblast activation protein inhibitor (FAPI)-based PET/CT imaging has become a popular modality in the evaluation of various cancers. Here, we present a case of MM where FDG avidity was notably absent and mild FAPI avidity, despite the lesion's typical anatomical location and clinical suspicion. This case highlights an uncommon scenario within the literature and underscores the variability in radiotracer uptake observed in MMs, challenging conventional imaging expectations and potentially impacting clinical management decisions.
黏膜黑色素瘤（MMs）是黑色素瘤的一种罕见亚型，起源于非皮肤部位的黑色素细胞，如头颈部、胃肠道和泌尿生殖道的黏膜。与皮肤黑色素瘤不同，MMs因其隐匿性往往出现较晚，导致预后较差。氟-18氟脱氧葡萄糖正电子发射断层扫描/计算机断层扫描（18F-FDG PET/CT）因其特征性的高FDG摄取，被广泛用于黑色素瘤的分期和监测。最近，基于成纤维细胞活化蛋白抑制剂（FAPI）的PET/CT成像已成为评估各种癌症的一种常用方法。在此，我们报告一例MM病例，尽管病变位于典型的解剖位置且临床高度怀疑，但FDG摄取明显缺乏，仅表现为轻度FAPI摄取。该病例突出了文献中一种不常见的情况，并强调了MMs中观察到的放射性示踪剂摄取的变异性，挑战了传统的影像学预期，并可能影响临床管理决策。
