B-cell peripheral neurolymphomatosis: MRI and ¹⁸F-FDG PET/CT imaging characteristics

Objective: To examine the MRI and ¹⁸F-FDG PET/CT imaging characteristics of peripheral neurolymphomatosis. Materials and methods: All institutional cases of neurolymphomatosis with an MRI or ¹⁸F-FDG PET/CT from 2000 to 2017 were retrospectively reviewed. Included cases were biopsy-proven neurolymphomatosis or lymphoma patients with clinical and imaging evidence of neurolymphomatosis that resolved after chemotherapy. Multiple imaging parameters and clinical characteristics were recorded. Results: There were 27 cases of B-cell neurolymphomatosis in 25 patients (18 M, 7 F; mean age 64.6 ± 10.0 years). Of the total cases, 85% (23/27) were biopsy-proven. Most were diagnosed after disease progression or recurrence (20/27, 74%), and presented with isolated nerve involvement (18/27, 67%). Bone marrow biopsy (17/19, 89%) and CSF cytology (16/23, 70%) were usually negative. On ¹⁸F-FDG PET/CT, neurolymphomatosis presented as a linear or fusiform (23/26, 88%), FDG-avid (average SUVmax: 7.1 ± 4.5, range, 1.5–17.0) mass, and on MRI as a T2-weighted hyperintense (21/22, 95%), enhancing (21/22, 95%), linear or fusiform mass (19/22, 86%), with associated muscle denervation (14/22, 64%). FDG avidity was significantly higher in patients with muscular denervation on MRI (mean SUVmax 8.2 ± 4.6 vs. 4.3 ± 2.3, p = 0.04). Conclusions: B-cell neurolymphomatosis most commonly manifests as T2-weighted hyperintense, enhancing linear or fusiform neural enlargement associated with muscular denervation on MRI, with intense FDG activity on PET/CT. It is most often an isolated site of disease, presenting after progression or recurrence. A familiarity with the imaging appearance of neurolymphomatosis can help refine the differential diagnosis, direct biopsy, and aid in accurate diagnosis.