Meta-analysis of the literature on 1946 cases of minor salivary gland tumors of the palate.

Minor salivary gland tumors are relatively rare and exhibit great diversity in terms of histopathology, localization, biological behavior and classification. The studies of significant case series report controversial data, mainly in terms of the proportion of benign versus malignant tumors and the relative frequency of histological types. Palate tumors are the most frequent, with an incidence of over 50%. The aim of the present study was to perform a meta-analysis to evaluate salivary gland tumors of the palate in terms of the proportion of malignant versus benign tumors, the frequency of the histological types and the data employed for statistical analysis. We analyzed a selection of international publications (1950-1999) of case series of minor salivary gland tumors of the palate, including our own series. The host institutions were classified into 3 categories: A) High Complexity Institutions (HCI), i.e. oncological reference centers and general hospitals that treat cancer patients; B) Medium Complexity Institutions (MCI); C) Low Complexity Institutions (LCI). Based on the main classifications, we joined categories and employed a simplified classification to analyze a total of 1835 cases in the literature and our own series of 111 cases (unpublish data). The results of the meta-analysis of the literature demonstrated that the data employed for statistical analysis depends on the type of host institution. The classification of institutions according to their level of complexity allowed for adequate interpretation of the previously published statistical data. Our interpretation of these studies suggests that the data on the percentage of malignant versus benign tumors and diversity of histological type must be obtained from series of low complexity institutions. LCI data are reliable whereas the HCI data are based on pre-selected cases, rendering the data unreliable.