False-negative FDG-PET in histologically proven extensive large cell bone marrow involvement in diffuse large B-cell lymphoma.

Abstract

A 69-year-old man presented with right axillary lymph node enlargement and B-symptoms (fever, night sweats, and weight loss). 18F-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) showed confluent right axillary and right cervical lymphadenopathy (Image 1A–C, arrows). Excisional right axillary lymph node biopsy revealed diffuse large B-cell lymphoma (DLBCL). Importantly, FDG-PET did not show any signs of lymphomatous disease in other locations, including the bone marrow. Axial FDG-PET with concomitant CT at the level of the posterior iliac crest was also negative for bone marrow involvement (Image 1D,E). Right posterior iliac crest bone marrow biopsy (BMB) was performed. Remarkably, despite the negative bone marrow FDG-PET findings, the bone trephine showed extensive bone marrow involvement, estimated at 50%, by the DLBCL (Image 1F–H [HE, original magnifications ×25/×200/×630, respectively] and Image 1I,J [CD20, original magnifications ×25/×200, respectively]). Recently updated guidelines on the Role of Imaging in the Staging and Response Assessment of Lymphoma consider FDG-PET more sensitive than BMB for the detection of bone marrow involvement, and that FDG-PET may only miss low-volume diffuse involvement of 10–20% of the marrow 1, 2. In addition, these guidelines mention that BMB is only needed for DLBCL if FDG-PET is negative and identifying a small cell (discordant) bone marrow involvement is important for patient management 1, 2. However, the presented case shows that FDG-PET can miss rather extensive large cell (concordant) bone marrow involvement in DLBCL. Therefore, BMB remains to play an important role in the evaluation of the bone marrow in DLBCL. Coronal (A), oblique (B), and sagittal (C) 18F-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) maximum intensity projections (MIPs) showing right axillary and right cervical lymphadenopathy, but no involvement of the bone marrow. Axial FDG-PET (D) with concomitant CT (E) of the posterior iliac crest showing no signs of bone marrow involvement. Hematoxylin and eosin (HE) (F,G,H, original magnifications 25×/200×/630×, respectively) and CD20 (I,J, original magnifications 25×/200×, respectively) stained bone marrow biopsy specimens showing extensive large cell (concordant) bone marrow involvement, estimated at 50% by the DLBCL. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]