5List of abbreviations 6Introduction 8

Salivary gland tumors are uncommon, and their epidemiology has not been well described. We conducted a descriptive epidemiologic study of parotid, submaxillary, and sublingual gland tumors newly diagnosed in Jefferson County, Alabama, hospitals from 1968 to 1989. Incidence rates were estimated with a population-based subset of cases diagnosed during the years 1979 to 1980, 1983 to 1984, or 1987 to 1988. Among 248 incident cases, 84.3% were benign and 15.7% were malignant. Eighty-six percent of cases arose in the parotid gland, and 14% arose in the submaxillary gland. No sublingual gland tumor was identified. The benign mixed tumor was the most frequent tumor (65.6%), followed by Warthin's tumor (29.2%). Mucoepidermoid carcinoma was the most frequent malignant tumor (51.3%). The average annual age-adjusted incidence rate per 100,000 was 4.7 for benign tumors and 0.9 for malignant tumors. Incidence rates for both benign and malignant tumors increased with age until ages 65 to 74 years and then declined. Benign mixed tumors occurred more frequently in female patients, whereas Warthin's tumors and malignant tumors occurred more frequently in male patients (P < 0.05). Warthin's tumor was rare in black patients (P < 0.001). We conclude that salivary gland tumors are an uncommon but epidemiologically diverse group of tumors. Their causes are also likely to differ.

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Multiple myeloma, a neoplasm of plasma cells, accounts for 15% of lymphatohematopoietic cancers (LHC) and 2% of all cancers in the US. Incidence rates increase with age, particularly after age 40, and are higher in men, particularly African American men. The etiology is unknown with no established lifestyle, occupational or environmental risk factors. Although several factors have been implicated as potentially etiologic, findings are inconsistent. We reviewed epidemiologic studies that evaluated lifestyle, dietary, occupational and environmental factors; immune function, family history and genetic factors; and the hypothesized precursor, monoclonal gammopathies of undetermined significance (MGUS). Because multiple myeloma is an uncommon disease, etiologic assessments can be difficult because of small numbers of cases in occupational cohort studies, and few subjects reporting exposure to specific agents in case-control studies. Elevated risks have been reported consistently among persons with a positive family history of LHC. A few studies have reported a relationship between obesity and multiple myeloma, and this may be a promising area of research. Factors underlying higher incidence rates of multiple myeloma in African Americans are not understood. The progression from MGUS to multiple myeloma has been reported in several studies; however, there are no established risk factors for MGUS. To improve our understanding of the causes of multiple myeloma, future research efforts should seek the causes of MGUS. More research is also needed on the genetic factors of multiple myeloma, given the strong familial clustering of the disease. ' 2007 Wiley-Liss, Inc.Key words: multiple myeloma; epidemiology Multiple myeloma is a malignancy of plasma cells that results in an overproduction of light and heavy chain monoclonal immunoglobulins. The specific immunoglobulin secreted by the malignant cell is the M-protein, named in reference to its monoclonal characteristics. It is found in the serum and/or urine of persons affected with multiple myeloma.

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