S5373 Endonephrology: Endoscopic Ultrasound-Guided Diagnosis of Renal Lymphoma

Introduction: Renal involvement of mucosa-associated lymphoid tissue (MALT) lymphoma, a subtype of non-Hodgkin lymphoma most commonly of gastric origin, is rare. Renal biopsy is typically percutaneous with ultrasound or computed tomography (CT) guidance. We present a novel approach of endoscopic ultrasound (EUS)-guided fine needle biopsy (FNB) as a minimally invasive diagnostic tool for renal MALT lymphoma. Case Description: A 77-year-old African American man with history of duodenal MALT lymphoma, prostate cancer, rectal adenocarcinoma, and systemic lupus erythematosus (SLE) presented for evaluation of a right renal mass seen on CT. PET imaging revealed a poorly circumscribed mass at the mid-pole of the right kidney and multifocal mediastinal and bilateral hilar lymphadenopathy with intense fluorodeoxyglucose uptake. EUS identified a 35 mm hypoechoic, heterogenous mass in the right kidney abutting the duodenal wall. A trans-gastric and trans-duodenal approach was used to make 3 passes with a 22-gauge biopsy needle. Pathology revealed mature B-cell lymphoma consistent with MALT lymphoma. Treatment with bendamustine/rituximab was initiated. Discussion: MALT lymphoma is of gastric origin in over 80% of cases. Renal involvement is exceedingly rare due to the kidney lacking native lymphoid tissue except in settings of chronic inflammation such as autoimmune states. MALT lymphomas have been described in association with autoimmune diseases with one prior case report documenting renal MALT lymphoma in a patient with SLE, hypothesized to result from uncontrolled lymphocyte activity causing malignant transformation. Renal lesions are often sampled through percutaneous biopsy guided by either ultrasound, due to its simplicity and efficiency, or by CT, due to improved visualization for smaller masses. However, size, cystic features, long skin-to-mass distances, upper pole location with hilar involvement, or body habitus are all factors that can limit these approaches. EUS-guided techniques using fine needle aspiration or FNB offer high resolution imaging and precise targeting of renal masses with difficult features or positioning. Feasibility and efficacy of these approaches have been well documented, and cytological diagnosis has shown high sensitivity and specificity. Fewer cases describe FNB which has greater diagnostic capacity due to histologic preservation, making it a promising minimally invasive technique for histopathologic evaluation of renal masses.