Background:Loss of heterozygosity, frequently observed during the development of many tumor types, also occurs in larynx cancer. This disease has a very complex genetic background, with numerous alterations involving oncogenes and tumor suppressor genes. The upper parts of the respiratory-digestive tract are exposed to many carcinogens, which can result in the appearance of multiple tumors or primary tumor relapses. The examination of normal-appearing tissues makes it possible to recognize genetic events occurring at early stages.Material/Methods: 65 larynx cancer patients were examined for loss of heterozygosity (LOH) on the 13q chromosomal arm, with the application of three microsatellite markers. The material from each patient consisted of blood, tumor, safe margin, and 1–2 clinically unchanged mucosal samples.Results: High frequencies of LOH in tumor tissues (49–64%) were observed in both studied chromosomal regions (13q14 and 13q34). The frequency of LOH in safe margin ranged from 12 to 31%. In normal-appearing mucosa, LOH was observed less frequently: 6–26% of informative cases.Conclusions: The data obtained from this investigation suggest that losses in the region of the 13q arm occur frequently during larynx cancer development. Moreover, they were observed not only in tumor tissues, but also in clinically unchanged mucosa. This could be a highly reliable predictor of the occurrence of relapse or second primary tumor in this anatomical site.

Keywords: Base Sequence, Chromosomes, Human, Pair 13 - genetics, Follow-Up Studies, Laryngeal Neoplasms - genetics, Laryngeal Neoplasms - pathology, Loss of Heterozygosity - genetics, Mucous Membrane - metabolism, Mucous Membrane - pathology, Base Sequence, Chromosomes, Human, Pair 13 - genetics, Follow-Up Studies, Laryngeal Neoplasms - pathology, Loss of Heterozygosity - genetics, Mucous Membrane - pathology