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Persistent FDG Avid Anterior Mediastinal Mass in the Setting of Treated Diffuse Large B-Cell Lymphoma FREE TO VIEW

Kevin Kane, MD; Jennifer Toth, MD; Christopher Gilbert, DO; Michael Reed, MD
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Penn State Milton S. Hershey Medical Center, Hershey, PA

Chest. 2013;144(4_MeetingAbstracts):634A. doi:10.1378/chest.1705083
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SESSION TITLE: Cancer Student/Resident Case Report Posters II

SESSION TYPE: Medical Student/Resident Case Report

PRESENTED ON: Tuesday, October 29, 2013 at 01:30 PM - 02:30 PM

INTRODUCTION: Non-Hodgkin Lymphoma (NHL) represents a diverse group of malignancies, with diffuse large B cell lymphoma (DLBCL) the most common subtype. Disease progression occurs in up to 50% of patients during the first 3 years after treatment in the rituximab era. Biopsy of the involved lymph node or mass is usually recommended to confirm relapse or exclude other conditions. We report an individual with Mycobacterium avium infection (MAI) diagnosed by video assisted thoracic surgery (VATS) biopsy of an anterior mediastinal mass suspicious for refractory lymphoma.

CASE PRESENTATION: A healthy, non-smoking 27 year old woman with worsening dyspnea was diagnosed with a large anterior mediastinal mass with left lung and left hilar involvement by chest CT. Transthoracic needle aspiration was non-diagnostic. Mediastinoscopy provided sufficient tissue to demonstrate DLBCL. She underwent six cycles of chemotherapy (R-CHOP) without incident. A restaging PET-CT scan three months after completion of chemotherapy showed considerable interval improvement in the size and FDG avidity of the mass. However, mild FDG uptake in the left anterior mediastinum and aortopulmonic window (Figure) was suspicious for refractory DLBCL. The locations of the lesions were determined to be high risk for transthoracic needle biopsy and were inaccessible by standard bronchoscopy. Left VATS biopsy of the anterior mediastinal mass was performed. Specimens from the left anterior mediastinum obtained via VATS showed no morphologic or immunophenotypic evidence of residual lymphoma. The tissue exhibited necrotizing granulomas. Microbiology studies revealed MAI.

DISCUSSION: Refractory or recurrent disease occurs frequently in lymphoma. However, other entities can masquerade as refractory or recurrent disease. Radiographic findings of mass lesions or FDG avidity are typically insufficient to establish a diagnosis of refractory disease. Tissue confirmation of potential relapsed or refractory DLBCL should be obtained before proceeding to further therapy. Here, VATS was utilized to access the anterior mediastinal mass not amenable to needle biopsy. The biopsy finding of active MAI not only obviated the need for treatment of suspected refractory DLBCL, but also demonstrated a process that required antimicrobial therapy.

CONCLUSIONS: In the setting of suspected refractory or recurrent lymphoma, tissue confirmation is vital. Mycobacterial infection can mimic the radiographic findings of recurrent disease.

Reference #1: Sehn et al. The revised International Prognostic Index (R-IPI) is a better predictor of outcome than the standard IPI for patients with diffuse large B-cell lymphoma treated with R-CHOP. Blood 109:1857-1861. (2007)

Reference #2: Castellucci P, Nanni C, Farsad M, et al. Potential pitfalls of 18F-FDG PET in a large series of patients treated for malignant lymphoma: prevalence and scan interpretation. Nucl Med Commun. 26:689-694. (2005)

DISCLOSURE: The following authors have nothing to disclose: Kevin Kane, Jennifer Toth, Christopher Gilbert, Michael Reed

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