S1745 Not All Colonic Masses Are Adenocarcinoma

Abstract

INTRODUCTION: Acute lymphoblastic leukemia (ALL) is a hematologic malignancy primarily affecting bone marrow, but with potential for blast cell to infiltrate extramedullary structures, most commonly the central nervous system. The gastrointestinal tract is not considered a primary site of disease involvement unless disease relapses. CASE DESCRIPTION/METHODS: A 20 year old man with celiac disease and Philadelphia negative, CD20+ B-cell ALL presented with abdominal pain. ALL was diagnosed 10 months prior and followed by treatment with AYA protocol of CALGB 10403 chemotherapy regimen, which consisted of vincristine, daunorubicin, pegaspargase, and prednisone. Rituximab was added due to CD20 + status. Regimen adjustment was required due to adverse effects of hepatitis and pancreatitis related to pegaspargase. After receiving 2 cycles of blinatumomab, a bone marrow biopsy supported clinical remission. Four weeks thereafter, the patient presented with severe abdominal pain, worse in the right lower quadrant. Exam revealed diffuse abdominal tenderness. Labs noted a mild normocytic anemia of 11.9 g/dL and thrombocytopenia of 119 K/MM3. Abdominal computed tomography measured 1.8 cm wall thickening in the appendix and cecum. Colonoscopy demonstrated multiple large, smooth, and firm polypoid masses in the cecum, with smaller satellite lesions in the ascending colon, an additional fungating mass in the distal ascending colon. Colonic mass biopsies demonstrated extensive leukemic infiltrate, consistent with B-ALL, which stained positive for PAX5, CD10, CD34, TdT, and negative for CD20. Chemotherapy and immunotherapy was reinitiated, with future plans for stem cell transplant. DISCUSSION: Although ALL with GI involvement is rarely reported, leukemic GI infiltration is identified in up to 25% of autopsies. As immune therapy has been theorized to leave extramedullary compartments vulnerable to incomplete disease eradiation, there is a potential for disease to exist undetected. Support for early endoscopy in patients undergoing immunotherapy and presenting with GI complaints may help to exclude GI involvement prior to declaring remission. A future prospective trial to identify risk factors for patients with ALL at high risk for GI infiltration would be valuable to determine those more likely to benefit from early endoscopic evaluation, and thus avoid unnecessary procedures in a population already at elevated procedural risk due to immunocompromised state and common presence of cytopenias.Figure 1.: Picture 1: CT abdomen/pelvis depicting cecal thickening of 18.47 mm.Figure 2.: Picture 2: A & B Colonoscopic findings of cecal masses, C. Colonoscopic findings of distal ascending colon mass.Figure 3.: Picture 3: A. Histology of leukemic infiltration in the colon, B. PAX5 positive immunohistochemistry staining, C. CD34 positive immunohistochemistry staining, D. TdT positive immunohistochemistry staining.