Primary extranodal and nodal non-Hodgkin's lymphoma. A survey of a population-based registry.

In a population-based registry, there were 580 patients with non-Hodgkin's lymphoma (NHL); 236 had primary extranodal lymphoma (41%). The initial localization of the primary extranodal lymphomas varied markedly, although 36% were primary gastrointestinal lymphomas. Histological classification was performed by a regional panel of pathologists according to the Kiel Classification and the International Working Formulation. Twelve per cent of the patients with nodal NHL had a localized disease in contrast to 40% with primary extranodal NHL. Low grade lymphomas were encountered in 30 and 10% of the patients with primary nodal and extranodal NHL, respectively. Recurrence-free survival rate for patients with localized low-grade malignancy and disseminated intermediate grade NHL is significantly better for extranodal lymphoma than for nodal NHL. Patients with disseminated high-grade extranodal NHL had the worst prognosis of all. We conclude that primary nodal and primary extranodal lymphomas should be considered as distinctive and separate entities.