To study the association of qat chewing with the occurrence of oral cancer, the frequency of oral cancer among whole body cancers and the patients' histories of tobacco consumption and qat chewing were examined in Yemen where qat chewing has been most popular. All primary malignant tumors listed in the surgical pathology files at Al-Thawra Hospital, University of Sana'a, in the year 2004 were analyzed, and the patients' histories of tobacco consumption and qat chewing were examined. A total of 649 cases of primary malignant tumors (348, 53.6% males and 301, 46.4% females) were extracted. Oral cancer was the most frequent body cancer in both males (17.2%) and females (19.6%). Squamous cell carcinoma (SCC) was the most frequent oral cancer (84%), and the tongue (42%), gingiva (23%) and buccal mucosa (20%) were the most common sites. Among the 119 patients with oral cancer, information on chewing habits and smoking was obtained in 92 patients (77.3%). There were 70 tobacco chewers (76.1%), 55 qat chewers (59.8%), and 22 smokers (23.9%). Simultaneous chewing of tobacco and qat was found in 48 cases (52.2%). The present survey has disclosed for the first time that oral SCC is the most frequent cancer in this study area in Yemen, and that the high relative frequency of oral SCC may be related to the habits of chewing tobacco and qat.

Objective: Podoplanin, a known lymphatic endothelial cell marker, has been reported to be expressed in various types of cancer. To elucidate the expression of podoplanin in precancerous lesions, we examined the immunohistochemical profiles of podoplanin in oral squamous epithelial lesions. Method: We studied a total of 298 foci of squamous cell carcinoma (SCC), carcinoma in situ (CIS), epithelial dysplasia, and hyperplastic and/or normal epithelial lesions by immunohistochemistry using D2-40. Results: There was no positivity for podoplanin in normal or hyperplastic epithelia, while all of the CIS and SCC foci stained positive. Approximately one third of the mild dysplasia foci (10 of 36 foci, 28%) and 80% of moderate dysplasia foci (78/98) showed grade 1 positive reactions (positive only in the 1st layer). Grade 2 reactions (up to 4th layer) were seen in 4 of 98 moderate dysplasia foci (4%), 29 of 74 CIS foci (39%), and 3 of 30 SCC foci (10%). Grade 3 reactions (to more than 5th layer) were found in 35 (47%) CIS foci and 26 (87%) SCC foci. Conclusions: The relationship between the present histological categorization and podoplanin grade was statistically significant. D2-40 expression is considered to be related to the severity of oral precancerous lesions.

The localization and biosynthesis of perlecan, a basement membrane-type heparan sulfate proteoglycan, were studied in developing tooth germs by using murine molars in neonatal and postnatal stages and primary cultured cells of the enamel organ and dental papilla to demonstrate the role of perlecan in normal odontogenesis. Perlecan was immunolocalized mainly in the intercellular spaces of the enamel organ as well as in the dental papilla/pulp or in the dental follicle. By in situ hybridization, mRNA signals for perlecan core protein were intensely demonstrated in the cytoplasm of stellate reticulum cells and in dental papilla/pulp cells, including odontoblasts and fibroblastic cells in the dental follicle. Furthermore, the in vitro biosyntheses of perlecan core protein by the enamel organ and dental papilla/pulp cells were confirmed by immunofluorescence, immunoprecipitation, and reverse transcriptase-polymerase chain reaction. The results indicate that perlecan is synthesized by the dental epithelial cells and is accumulated in their intercellular spaces to form the characteristic stellate reticulum, whose function is still unknown.