Diffuse pulmonary uptake on FDG-PET with normal CT diagnosed as intravascular large B-cell lymphoma: a case report and a discussion of the causes of diffuse FDG uptake in the lungs

Abstract

A 71-year-old woman was admitted to our hospital with asthenia, weight loss, fever, cognitive impairment and shortness of breath. Physical examination showed hemiparesis and cerebellar ataxia. There was no superficial lymphadenopathy. Blood tests showed raised levels of C-reactive protein and lactate dehydrogenase. Bone marrow aspiration and biopsy were negative. [18F]fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) showed intense uptake within a right apical nodule and intense and diffuse uptake of FDG in the lungs without corresponding structural CT abnormality. Lung biopsy showed intravascular large B-cell lymphoma (IVLBCL). FDG-PET findings in IVLBCL and causes of diffuse FDG lung uptake with and without CT abnormalities are discussed.

Figure 1

(a) Intense and diffuse lung uptake without CT structural abnormality on FDG-PET/CT. Accumulation of FDG within the lungs is homogeneous, with bilateral high-grade uptake in the posterior and inferior aspect of the lungs and diffuse low-grade uptake in the remainder of the lungs. (b) Intense and focal FDG uptake in a right apical nodule on a background of diffuse low-grade FDG uptake in normally aerated lungs. (c) maximum intensity projection (MIP) image demonstrating diffuse lung FDG uptake and focal uptake in a right apical lung nodule.

Figure 2

FDG-PET/CT evaluation after 2 cycles of chemotherapy demonstrated a marked decrease in bilateral lung uptake with a persistent low-grade homogeneous uptake and resolution of the right apical nodule. Top row is a fused image transverse section of the lungs and MIP, status post-chemotherapy. Bottom row is a fused image transverse section of the lungs and MIP, status pre-chemotherapy.

Figure 3

(a) The large atypical lymphoid cells are entirely located in the lumina of the septal capillary bed in the lung (hematoxylin–eosin, original magnification ×400). These lymphoid cells have irregular nuclear contours, coarse chromatin, prominent nucleoli, and relatively abundant basophilic cytoplasm. (b) Immunohistochemical features of the IVLBCL. The neoplastic cells in the lung are strongly and diffusely positive for CD20 (original magnifications ×200). (c) The neoplastic cells demonstrate a high proliferation index as revealed by MIB-1 (Ki-67) (original magnification ×200).

Figure 4

Brain MRI with axial diffusion-weighted images (b, e), axial fluid-attenuated inversion recovery (FLAIR) weighted images (a, d), and axial contrast-enhanced T1-weighted images (c, f) showed subacute bilateral scattered brain infarcts affecting multiple vascular territories, carotid (a–c arrows) and vertebro-basilar (d–f), with cortical, subcortical and deep lesions (a, d arrows). Note the high signal of the left middle cerebellar peduncle without restriction of the apparent diffusion coefficient testifying to the different age of the ischemic lesions (d arrowhead, e). Strong scattered abnormal gyriform (c, empty arrows) and nodular (c, white arrow) enhancement is seen.