Distribution and prognostic significance of cell cycle proteins in squamous carcinoma of the larynx, hypopharynx and adjacent epithelial hyperplastic lesions.

Alterations of cell cycle proteins contribute to the development and biological behaviour of malignant tumours. We evaluated the distribution and prognostic significance of immunohistochemically detected proteins p53, p21, Rb, and cyclin D1 in 101 laryngeal and hypopharyngeal squamous cell carcinomas (SCC) and adjacent epithelial hyperplastic lesions (EHL). Protein expression was correlated with tumour grade and stage. Varying patterns of protein expression were found in SCC. A significant correlation (p<0.05) was found between Rb expression and tumour grade. Different grades of EHL exhibited randomly distributed p53 and cyclin D1 positive cell clusters with no association to the pattern of their expression in SCC. Our study demonstrated derailment of cell cycle regulation in almost all cases of SCC of the larynx and hypopharynx. However, only cyclin D1 expression had an independent prognostic value for cancer-specific survival. The results also suggest that Rb gene inactivation, although rare, might be more important in the development of SCC than previously thought.