Primary colonic lymphoma. Clinical presentation, histopathologic features, and outcome with combination chemotherapy.

Primary colonic lymphomas are rare, but we identified 15 cases at our institution between 1973 and 1992. They comprised 5.8% of all cases of gastrointestinal lymphoma (15 of 259) and 0.16% of all cases of colon cancer (15 of 9,193) during the last 20 years. The most common presenting symptoms were abdominal pain and weight loss (40% each). In seven patients (47%), a palpable abdominal mass was noted on the initial physical examination. The most frequent site of involvement was the cecum (73%). Histologically, six (40%) were classified as high-grade and nine (60%) as intermediate-grade non-Hodgkin's lymphoma. The tumors usually presented at an advanced stage: in 13 of 15 patients (87%), the lymphoma had spread to the adjacent mesentery, the regional lymph nodes, or both when first diagnosed. The 5-year survival rate was 27% for all patients and 33% (4 of 12) for patients treated with combination chemotherapy. Two patients relapsed after 8 years of complete remission. Primary colonic lymphomas have an aggressive behavior and only a marginal response to surgery and combination chemotherapy.