In a retrospective analysis of cluster of differentiation 44 (cell surface molecule) (CD44) mRNA and CD44 protein expression, as putative stem cell markers on tumour material from patients with early laryngeal carcinoma, the intertumoural heterogeneity of the stem cell density as an important factor for local tumour control after radiotherapy could be shown for the first time in a clinical dataset (de Jong et al., 2010). The gene discussed is CD44; the disease is neoplasm.