[The relationship between the doubling time of human lung tumor volume and the labelling index]

The value of the labelling index (incubation with H3-thymidine) was compared with the doubling time of tumour volume (by repeated roentgenograms) for 3 tumours of human lungs: two squamous cell carcinomas taken at various differentiation levels and a hamartoma. The minimum doubling time (178 days) was shown for the squamous cell carcinoma with a lower differentiation level and the greatest labelling index value (19.0%). Hamartoma (a non-malignant tumour of lung) displayed the longest doubling time (1250 days) and the least labelling index value (3.8%).