A 76-year-old man presented with shortness of breath. Computed tomography revealed ground-glass opacity and interlobular thickening in the right lower lobe. Blood examination showed elevated levels of white blood cell count and lymphocytes. Bone marrow aspiration revealed low-grade follicular lymphoma. Histopathological examination of the surgical lung biopsy from the right lower lobe demonstrated usual interstitial pneumonia and scattered aggregation of lymphocytes with poorly formed non-necrotizing granuloma. An 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET-CT) did not show intense uptake in areas other than the right lower lobe. We concluded that the granuloma in the lung was presumed to be a sarcoid reaction associated with bone marrow follicular lymphoma, and the intense 18F-FDG uptake in the right lower lobe might have been due to a sarcoid reaction. Immunohistochemistry or other genetic examinations are important even if 18F-FDG uptake on PET-CT seems to be a false-positive because of the possibility of a sarcoid reaction.
Keywords: Follicular lymphoma.