Comparative histochemical study of Bowen's disease and actinic keratosis: preserved normal basal cells in Bowen's disease

The degree of DNA-instability as revealed by immunohistochemical staining w ith anti-cytidine antibody after acid hydrolysis (DNA-instability test) has been recently used as a marker of malignancy. This technique was applied t o examine 17 skin tissue samples of Bowen's disease, 47 of actinic keratosi s, 15 of squamous cell carcinoma, 5 of seborrheic keratosis, and 10 of norm al skin. All benign neoplastic cells of seborrheic keratosis and normal epi dermal cells were negative. On the other hand, all cancer cells were positi ve with the DNA-instability test, indicating their malignancy, but all basa l cells in Bowen's disease were completely negative. Compatible with this r esult, the basal cells in Bowen's disease were characteristically normal as evident in other histochemical examinations. Thus, they were negative with p53 immunohistochemistry, with normal signals of chromosome 17 in situ hyb ridisation and argyrophilic nucleolar organiser region, and showed slightly enhanced proliferative activity as revealed by proliferating cell nuclear antigen immunohistochemistry. Immunohistochemical staining with 34 beta E12 (monoclonal antibody against cytokeratins 1, 5, 10, and 14), which stains all normal epidermal keratinocytes including basal cells, showed that only the basal cells of Bowen's disease stained strongly and homogeneously, whil e all cancer cells in the upper layers of Bowen's disease and all layers of actinic keratosis were only sporadically or weakly stained. Staining with 34 beta B4 (monoclonal antibody against cytokeratin 1), which recognises th e whole epidermis except for the basal layer in the normal epidermis, showe d that the basal cells in the Bowen's disease were completely negative, and lower layer cells in the actinic keratosis and upper layer cells in Bowen' s disease were only sporadically stained positive, although the superficial layer cells in actinic keratosis stained strongly and homogeneously. Our f indings clearly indicate that the basal cells in Bowen's disease are normal . In support of this conclusion, the same cells showed normal morphology on electron microscopy with preserved basement membrane, although the latter was often damaged in actinic keratosis.