Primary Pulmonary Diffuse Large B-Cell Lymphoma - a Rare Case Report

Background:

Diffuse large B cell lymphoma (DLBCL) is an aggressive hematological malignancy, and a common histological form of non-Hodgkin's lymphoma. However, its extra-nodal presentation is seen in 30-40% of cases with involvement of gastrointestinal tract, skin, testes, adrenals and bone. ( Lugogo NL et al., 2006) A pulmonary manifestation is an extremely rare entity. We present an atypical case of DLBCL presenting as pleuritic chest pain with imaging consistent with bilateral pulmonary nodules suggestive of metastasis.

Case description:

A healthy 87 year old male former smoker with a history of type 2 diabetes mellitus, hypertension presented to the emergency department with pleuritic chest pain. There was no associated cough, shortness of breath, palpitations, nausea, dizziness or diaphoresis. No recent infections or B symptoms. He had a good appetite. He had prostate cancer 20 years ago and had a radical prostatectomy.

Upon presentation, work up showed mild anemia (Hb 11.1 g/dL). Cardiac work up for chest pain was unremarkable. Chest X-Ray revealed mass like opacities in each lung with largest in left mid lung measuring up to 6 cm. CT chest with IV contrast revealed multiple lung nodules bilaterally with 2 largest in left upper lobe measuring 5.6 x 3.7 cm and 5.7 x 3.3 cm. Multiple other small nodules are present in both lung fields consistent with diffuse lung metastasis. No lymphadenopathy was noted. (Image 1) PET CT scan was significant for bilateral FDG avid lung lesions. No evidence of other FDG avid disease.

CT guided biopsy of the left lung mass surprisingly revealed diffuse large B cell non-Hodgkin's lymphoma, non-germinal center type. (Image 1) Immuno-histochemistry showed atypical lymphocytes positively stained with CD20, BCL6, BCL2, PAX5 and MUM1. C-myc had 50% positivity. Ki67 had 90% proliferative index. FISH analysis was negative for MYC, BCL2 and BCL6; hence there was no double hit lymphoma detected.

According to Lunago classification, patient had advanced stage disease with IPI (prognosis index) of 2. His ECOG PS score was 0. He was initiated on R-Pola-CHP. Given his age, Cyclophosphamide and Adriamycin doses were reduced as done with R-mini CHOP. Vincristine was avoided given neurotoxicity.

Discussion:

Primary pulmonary B-cell lymphomas (PP-BCLs) represent less than 3-4% of all extra-nodal NHL. They primarily affect the lung without evidence of extrapulmonary disease at the time of diagnosis. PP-DLBCL accounts for only 10% cases of PP-BCLs. ( Sanguedolce et al., 2021)

Most cases have atypical presentation. Likewise, in our patient, he manifested with atypical chest pain without any B symptoms. Radiographic imaging can show variable findings of consolidation, single/multiple nodules, reticular interstitial infiltrate or bilateral ground glass opacities. In view of the insidious onset and lack of specificity in clinical symptoms, primary pulmonary lymphomas are frequently misdiagnosed as refractory pneumonia, lung abscess, asthma, primary lung cancer, or lung metastasis. ( Liu et al., 2020)

Patients with DLBCL are typically treated with R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone). However, with this regimen, only 60% of patients are cured and the rest might relapse. In the POLARIX phase 3 trial, polatuzumab vedotin (a monoclonal antibody to CD79b ubiquitously expressed on B cells) combined with R-CHP significantly improved 2 year progression-free survival compared to the routine R-CHOP therapy in previously untreated DLBCL patients. ( Tilly et al., 2022) Given our patient's advanced stage disease, he was initiated on the Pola-R-CHP regimen. Doses of cyclophosphamide and doxorubicin were reduced as per the R-mini CHOP dose-reduced regimen for a physically fit elderly individual. Patient continues on therapy at the time of this abstract.

In conclusion, primary pulmonary DLBCL is a rare entity with only a few case reports in literature. It should be considered in patients presenting with large pulmonary masses, mimicking metastatic disease.