18F-FDG PET/CT demonstration of diffuse lymphohistiocytic granulomatous vasculitis

Surveillance FDG PET/CT was performed in a 75-year-old woman with history of melanoma and colon cancer. She had rash and erythematous papules on the forearms, elbows, knees, and thighs and then developed right-leg weakness, difficulty with fine motor movement, and ptosis. Chest CT identified a right-lung spiculated nodule. Skin and pulmonary nodule biopsies showed lymphohistiocytic infiltrate with granulomatous features, without lymphoid cells, metastatic carcinoma or melanoma cells, or microorganisms. Epstein-Barr immunostain result was negative, making lymphomatoid granuloma unlikely. The inflammatory process involved the peripheral vasculature on FDG PET, and given the related neuropathy, findings were compatible with granulomatous vasculitis.