D110-10 The Space Between: An Atypical Presentation of Mediastinal Gray Zone Lymphoma

Introduction Mediastinal Gray Zone Lymphoma (MGZL) is a rare lymphoid neoplasm with an incidence of 0.53 per million person-years. MGZL typically presents in young females as a mediastinal mass with a variable B cell immunophenotype, with intermediate features between Primary Mediastinal B-Cell Lymphoma (PMBL) and classic Hodgkin’s lymphoma (CHL). Greater awareness of compatible clinical and radiographic features is essential to improve outcomes for this rare and aggressive malignancy. Case An 18-year-old female with no significant medical history presented to clinic with complaints of dyspnea, cough, hoarseness, lymphadenopathy (LAD), night sweats and a 30-lb unintentional weight loss. Labs revealed a protein gap, elevated inflammatory markers, leukocytosis, mild anemia, and thrombocytosis. Computed tomography (CT) scan of the chest revealed a mediastinal mass with central venous narrowing, diffuse LAD, and cavitary pulmonary lesions. She was admitted to another institution for evaluation via robotic bronchoscopy with transbronchial biopsy of the right upper lobe lesion and endobronchial ultrasound transbronchial needle aspiration of lymph nodes, which were non-diagnostic. She was diagnosed with pneumonia and scheduled for follow-up. Two months later, she developed progressive dyspnea, palpitations, and night sweats. Work up revealed extensive LAD, a 12 cm anterior mediastinal mass suspicious for lymphoma, cavitary lung lesions, bilateral pleural effusions, and a moderate pericardial effusion (Figure 1). Rheumatologic and infectious workups were unrevealing. Axillary lymph node biopsy and peripheral flow cytometry were nondiagnostic. The patient declined repeat biopsy. Three months later, she presented with worsening dyspnea, weakness, and cough. Positron Emission Tomography-CT revealed enlarging pleural effusions with bilateral compressive atelectasis, a hypermetabolic anterior mediastinal mass with extensive LAD and necrosis, consistent with progressive malignancy. Bilateral thoracenteses showed chylous effusions, with lymphangiogram noting intact thoracic duct. IR-guided left cervical lymph node biopsy was diagnostic of MGZL; CD45+, CD30+, CD15+, PAX5+, CD19+, CD20+, CD79a-, OCT2-, and BOB1-, CD-10-, BCL6+, MUM1+, PD-L1+. She was treated with Da-EPOCH-R and is now in clinical remission, with radiographic improvement of cavitary lesions. Discussion MGZL is a rare primary B-cell lymphoma with immunotypic and morphologic features between PMBCL and CHL. While this presentation had classic mediastinal lymphoma symptoms, the cavitary lung lesions were less typical and broadened the differential to include infectious processes and non-hematologic malignancies. The simultaneous expression of some B cell markers along with those more typical of CHL is diagnostic of this condition. To our knowledge, this is the first reported case of MGZL presenting with cavitary lung lesions.