S1798 Composite Lymphomas in the Colon: Two Separate Entities, Treated as One

Abstract

INTRODUCTION: Composite lymphoma (CL) is defined as two histologically distinct variants of malignant lymphoma occurring in the same organ or mass. Our case describes an asymptomatic patient with two extranodal B-Cell lymphomas discovered after routine colonoscopy. Further, we discuss pathogenesis and treatment philosophy of follicular lymphoma and marginal cell lymphoma. CASE DESCRIPTION/METHODS: A 62 year old Japanese female with multiple medical morbidities including cirrhosis and hypothyroidism presented for surveillance colonoscopy. On presentation, patient denied any fever, chills, night sweats, unintentional weight loss, hematochezia, or melena. Colonoscopy revealed multiple sessile polyps, 2−5 mm in size. H&E and immunohistochemical staining of specimens demonstrated grade 3A follicular lymphoma with 100% follicular pattern and positron emission tomography/computed tomography (PET/CT) demonstrating a prominent, isolated pericaval lymph node. Per NCCN guidelines for follicular lymphoma grade 3A, stage II (non-contiguous), observation with follow up PET/CT and colonoscopy was recommended. Repeat colonoscopy after 6 months revealed multiple polyps with demonstrating extranodal marginal zone b-cell lymphoma of Mucosa-Associated Lymphoid Tissue (MALT). The diagnosis of MALT type lymphoma was rendered based on histologic patterns of infiltration, the cellularity of the infiltrate, their locations, presence of clear cells, and immunostaining. Of note, repeat PET/CT was negative for lymphadenopathy. 6 months later, another colonoscopy was performed, and 6 more polyps were biopsied. Histological examination was consistent with tubular adenomas and follicular lymphoid proliferation. Given that she was clinically stable with minimal disease, plan was to continue monitoring with colonoscopy and PET/CT annually. DISCUSSION: CLs are defined as 2 or more morphologically and/or immunophenotypically different components in the same anatomic site. They can arise synchronously or metachronously. CLs are rare, with a frequency ranging from 1 to 4.7% of lymphoma cases. More rarely, CL has seldom been witnessed in the gastrointestinal tract. To our knowledge, this is the first case reporting composite follicular lymphoma and extranodal marginal zone b-cell lymphoma of MALT in the colon. Current literature suggests the components of CLs progress as separate entities and treatment should be focused on the component with the least favorable prognosis.