Extranodal lymphoma: a comparative study

Background: The incidence of extranodal non-Hodgkin's lymphoma (NHL) is increasing worldwide. The epidemiology of NHL in the Middle East is largely unknown. Patients and methods: We evaluated all cases of NHL diagnosed at our institutions between 1998 and 2003 according to the site of presentation and their classification into primary nodal and primary extranodal NHL using strict criteria. Extranodal cases and early stage primary nodal cases were compared in terms of clinical characteristics and treatment outcomes. Results and discussion: There were 422 NHL cases diagnosed between January 1998 and December 2003, among which 97 cases (23%) were primary nodal, 132 (31%) were early nodal, and 193 (46%) were disseminated primary nodal. In general, there was a male preponderance of primary nodal cases (63% versus 44%; p=0·007). There was a higher prevalence of primary nodal cases in Arabs than in Asians: Kuwaiti Arabs, 50%; other Arabs, 46%; and Asians, 11%. There was a different distribution of histologic subtypes between primary nodal and extranodal NHL (p=0·001). The most common histologic subtype among extranodal cases was diffuse large B cell lymphoma, which accounted for 71% (69) of cases. The most common anatomic site involved was the gastrointestinal tract, which accounted for 45% of all cases. The difference in event-free survival between nodal and extranodal low-grade NHL was not statistically significant (p=0·17). Primary nodal high-grade lymphomas show an overall survival than the primary extranodal disease (p=0·003). Conclusion: We conclude that extranodal NHL is common among patients of Arabic descent. Diffuse large B cell lymphoma is the most common histologic subtype and often involves the gastrointestinal tract. Patients with aggressive primary extranodal NHL have lower overall survival than patients with early primary nodal disease.