Basal layer reactivity in hyperplastic and metaplastic lesions of the bronchi as studied by lectin histochemistry

The relationship between squamous metaplasia and squamous cell carcinoma of the bronchi has been the subject of controversy. We investigated basal cell hyperplasia, stratification, squamous metaplasia, and squamous cell carcinoma by means of lectin histochemistry with peanut agglutinin (PNA), Ulex europeus agglutinin-I, soybean agglutinin, and Dolichos biflorus agglutinin for all normal basal cells that are reactive. A basal layer stained with PNA was observed in basal cell hyperplasia, stratification, and squamous metaplasia, but this layer was not exhibited by squamous cell carcinoma. In hyperplasia and metaplasia, PNA staining was biased toward the lowest (basal) layer, whereas staining for the other lectins was more uniformly distributed across the layers. A PNA-positive basal layer may be important for the morphologic reversibility of the bronchial mucosa in hyperplastic and metaplastic lesions, and destruction of this layer may be associated with a progression from metaplasia to squamous cell carcinoma.