Lung parenchymal involvement of primary bone marrow follicular lymphoma: a rare case study

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.