LAUSR

Necrobiotic xanthogranuloma (NXG) is a rare, chronic, progressive non-Langerhans cell histiocytosis. Previous reports indicate that periorbital involvement and skin and subcutaneous nodules are the most frequent presentation [1–3]. We report here NXG involving multiple organs, including some unusual F-fluorodeoxyglucose (F-FDG) avid NXG locations. A 40-year-old man with a 6-month history of asymptotically increasing, multiple, purplish-red skin nodules was admitted to our hospital. Histopathological examination of skin biology specimens from the right waist showed diffused lymphocytic infiltration (i, black arrow) in the dermis and subcutaneous tissue, which were the primary areas with extensive necrobiosis, as well as a prominent granulomatous infiltrate (i, red arrow). Combined with clinical and pathological examination, the final diagnosis was NXG. F-FDG positron emission tomography/computed tomography (PET/CT) scan was recommended to establish a clear diagnosis of possibly a systemic tumor disease and malignancy after histological diagnosis. The maximal intensity projection (MIP, a) image shows abnormally intense FFDG uptake in the skin and subcutaneous tissues of multiple locations (d). Interestingly, widespread abnormal F-FDG-avid areas are noted along the vessels (a, black arrows) and scrotum (a, red arrows), which were rare sites in previous reports. Lesions were also present in the muscles (a, black arrowheads), lung (b), and myocardium in the right atrium (c), with an SUVmax of 14.1. Due to the lack of a uniform treatment protocol, a therapeutic strategy depending on current case reports and reviews was given [4]. The patient was then treated with chemotherapy, including cyclophosphamide, vincristine, and prednisone, combined with lenalidomide for 2 months; the multiple purple-red nodules in the whole body of this patient were smaller and reduced than before, and the follow-up F-FDG PET/CT showed that systemic lesions improved (MIP, h) and no FDG-avid lesions were detected in the lung (e), myocardium (f), and subcutaneous tissues (g). Our case showed that F-FDG PET can detect multiple systemic lesions that some are otherwise not visualized by routine radiological modalities, such as perivascular lesions. Moreover, monitoring the therapeutic effect using F-FDG PET/CT is a critical aspect of clinical treatment.