The incidence of lymphoma in the US and Puerto Rico among 13,600 patients is reported by histologic subtypes according to the Working Formulation. The most frequent histologic types were intermediate grades (five per 100,000 among whites, three per 100,000 among blacks, and two per 100,000 among Puerto Rican Hispanics). Low-grade types were next in frequency (2.7 per 100,000 in whites, 1.5 per 100,000 in blacks, and one per 100,000 in Puerto Rican Hispanics). More than 95% of patients had lowor intermediate-grade lymphomas, and of these, intermediate-grade lymphomas occurred in 65% of patients. High-grade types were infrequent in all ethnic groups. The incidence among men was significantly greater than among women in all ethnic groups. There was a distinct peak for small noncleaved cell type among white boys but not girls. For all other histologic types, there was a conspicuous absence of a young adult component, with incidence increasing steadily with age. No evidence for seasonal fluctuation in month of diagnosis was found. This delineation of incidence by histologic groupings, sex, and ethnic group will facilitate future studies using the Working Formulation.
Cancer 592357-861, 1987. HE CLASSIFICATION OF LYMPHOMAS has evolved over T the last 30 years. In the past, morbidity and mortality statistics have been based on three major categories: lymphosarcoma, reticulum cell sarcoma, and giant follicular lymphoma.' In 1966, Rappaport proposed a new classification that was amenable to use by others and had prognostic implications.* The Rappaport system has undergone revisions as additional entities have been recognized. By the late 1970s, at least six histopathologic systems for classifying lymphomas were recognized.*-I2 The National Cancer Institute (NCI) undertook a multi-institutional comparative study of the systems that resulted in a classification system called the Working F0rmu1ation.l~ This study reports lymphoma incidence based on cases that have been reported to the Surveillance, Epidemiology, and End Results (SEER) program of the NCI and regrouped into histologic subtypes consistent with the Working Formulation.