LAUSR

A 51-year-old gentleman with no significant past medical history presented to a gastroenterologist for dyspepsia, chronic diarrhea, and 15-pound unintentional weight loss over 5 months. His physical examination was normal with no evidence of any abdominal masses or lymphadenopathy. A complete blood count showed: white blood count 2.79 (cid:1) 10 3 / μ L, hemoglobin 12.7 g/dL, hematocrit 36.9%, mean corpuscle volume 91.8 fL, and platelets 160 (cid:1) 10 3 / μ L. Anti-nuclear antibodies (ANA) testing was positive but further testing was negative for anti-Smith and anti-dsDNA antibodies. A colonos-copy was performed, and nodular mucosa was identified at the junction of the hepatic flexure (Image 1A), and this area was biopsied. Histologic sections show an extensive, destructive lymphocytic infiltrate involving the lamina propria, and colonic epithelium of all biopsy fragments (Image 1B,C). The lymphocytes are small to medium-sized with a round to slightly irregular nuclei, condensed chromatin, inconspicuous nucleoli, and scant cytoplasm. Immunochemical stains show that the lymphocytes are positive for CD3, CD56, CD7, and CD117 (weak) and negative for CD4, CD8, CD10, CD5, CD2, CD25, CD30, TdT, lysozyme, BetaF1, T-cell receptor (TCR)