[Marijuana and malignant tumors of the upper aerodigestive tract in young patients. On the risk assessment of marijuana].

Advocates of free distribution of marijuana and hashish describe these drugs as harmless. Several experimental in-vitro and in-vivo studies have shown the mutagenic and carcinogenic properties of tetrahydrocannabinol. Several carcinogenic polycyclic aromatic hydrocarbons have been extracted from tar of marijuana pipes. Tetrahydrocannabinol also inhibits the function of the immune system. T-cell lymphocyte counts are lower in chronic marijuana smokers compared to nonsmokers. Phytohaemagglutinin stimulation of lymphocytes as well as phagocytosis by polynucleic granulocytes is decreased. The number of young patients between 20 and 40 years with squamous cell carcinoma of the oral cavity, tongue, and pharynx is rapidly increasing. In the past seven years 34 young patients with squamous cell carcinomas have been treated at this institution. All were chronic marijuana smokers. Due to the often extensive field cancerisation, success of cancer therapy is limited in oral and pharyngeal cancers. Marijuana and hashish cannot be considered harmless. Education of the public about the carcinogenic properties of inhaled substances should include marijuana and hashish.