Thesis (Ph.D.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Oral and Maxillofacial Pathology

Oral cancer is the 11th most common malignancy in the world and the sixth most common type among all head and neck cancers with an annual incidence of about half a million new cases and around 300,000 death each year (1%{u2013}2% of all cancer death). It represents about 85% of all head and neck cancers. Among all oral cancers, squamous cell carcinoma accounts for 90% of them. Field cancerization is a relatively new terminology in the field of cancer, it indicates that when cancer develops in a tissue, a group of genetically altered clones of cells in adjacent clinically normal tissue occur, which are prone to the development of synchronous and metachronous tumors. The field cancerization theory also emphasizes the high probability of recurrences in patients with head and neck squamous cell carcinoma. Numerous factors have been implicated in the etiology of oral cancer. Through years, the use of tobacco, alcoholic beverages, smokeless tobacco and betel quid were considered well-known risk factors for oral squamous cell carcinoma development. However, minimal worthy studies were performed to investigate the effect of cannabis smoking on oral cancer development. In our study we aimed to investigate the changes that occur in the oral mucosa of cannabis smokers and compare them to cigarette smokers and non-smokers. Three groups of subjects were included in our study (33 in each group); cannabis and cigarette smokers, cigarette smokers and non-smokers. The mucosal biopsy was examined by routine H&E techniques. Furthermore, immunohistochemical expression of p53 was studied in all cases

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