1648 A Rare Case of Primary Colonic Lymphoma With Paraneoplastic Hypercalcemia

Abstract

INTRODUCTION: Primary colonic lymphoma (PCL) is a rare malignancy accounting for 1% of all gastrointestinal (GI) lymphomas and 0.1-0.5% of all colorectal malignancies. 15% of Non-Hodgkin Lymphoma develop hypercalcemia at some point during their clinical course but rarely symptomatic at the time of diagnosis. We report a rare case of symptomatic hypercalcemia from an ascending colon mass which was diagnosed as Diffuse large B cell lymphoma (DLBCL). CASE DESCRIPTION/METHODS: A 63-year-old male with history of type II Diabetes mellitus and hypertension presented with worsening confusion over a week. He also endorsed weight loss of 35 lbs in a month, intermittent right sided abdominal pain, constipation and dark colored stools on multiple occasions. He had a normal colonoscopy 5 years ago. Physical examination showed stable vital signs and hard palpable mass with ill-defined borders in the right flank. Labs were significant for Hemoglobin 8.2 g/dL, Creatinine 3.7 mg/dL, Calcium 13.1 mg/dL and ionized calcium of 7 mg/dL. Liver function tests and serum ammonia were normal. Computed tomography (CT) scan of abdomen showed 16 × 15 × 15 cm exophytic mass with central necrosis arising from the distal ascending colon (Figure 1). Colonoscopy (Figure 2) mediated biopsy was consistent with DLBCL. Bone marrow biopsy and PET- CT scan were negative for extracolonic lymphoma. A diagnosis of PCL was made based on Dawson’s criteria. He underwent a right hemicolectomy. Grossly the mass measured 20 × 18 × 14 cm with a necrotic center eroding the colonic mucosa (Figure 3). He was started on combination chemotherapy (R-CHOP regimen: Rituximab, Cyclophosphamide, Doxorubicin, Vincristine, Prednisolone) and Lenalidomide was added as his DLBCL was ABC (Activated B cell) type. Work up for hypercalcemia showed suppressed PTH levels, normal PTHrP, normal 25 OH Vitamin D and elevated calcitriol, consistent with increased production of calcitriol as the cause. DISCUSSION: Cecum is the most common site for PCL (60 – 75%), followed by rectosigmoid region (8.5 – 35%). This patient had mass in distal ascending colon which is an unusual location. Immunosuppression and Inflammatory bowel disease are the known risk factors for PCL, but often none could be identified. Hypercalcemia in NHL is mostly due to extrarenal production of 1,25-dihydroxyvitamin D facilitated by the 1α-hydroxylase enzymes in the macrophages that surrounds the malignant lymphocytes. In most series, surgery followed by multiagent chemotherapy (R-CHOP) has led to improved outcome.