[Proliferation kinetics of bronchioloalveolar tumorlets]

Bronchiolo-alveolar tumorlets--mostly clinically asymptomatic--generally are noticed as "contingent findings" in the diagnoses of interstitial fibrosing lung diseases. The growth fraction of these epithelial proliferates in the WHO classification summarized in the group of tumor like lesions was explored by immunohistochemical stainings with the PCNA and Ki67 (MIB1) antibodies and correlated with (pre-) neoplastic lesions of the lung. The proliferation indices varied between 0.029 to 0.67 (MIB1) and 0.057 to 0.81 (PCNA). Depending on the main disease the observation of cuboid metaplasias, areas of bronchiolization via tumorlets in inactive interstitial lung fibrosis up to bronchiolo alveolar tumorlets following interstitial lung disease after cytostatic treatment showed increasing proliferation indices. Accordingly to prencoplastic changes of the bronchial epithelium the findings suggest that interpretation of bronchiolo alveolar tumorlets as basic cells of malignant peripheral lung tumors seems to be possible. The value of these findings in relationship to the associated interstitial lung disease is discussed in the context of reflections related to the formal pathogenesis of so called scar cancer.