Pulmonary cystic keratinizing squamous cell lesions of rats after inhalation/instillation of different particles

Cystic keratinizing squamous cell lesions from three inhalation studies (study A, B, C) and one intratracheal instillation study (Study D) in rats were reclassified and a certain number of lesions examined immunohistochemically for PCNA (proliferating cell nuclear antigen) as a marker of cellular proliferation. The following classification was used: squamous cell metaplasia with marked keratinization, keratinizing cyst, cystic keratinizing epithelioma, cystic keratinizing squamous cell carcinoma, keratinizing squamous cell carcinoma and non-keratinizing squamous cell carcinoma. In study A (inhalation of coal oven exhaust and subcutaneous injection of a high dose of DB (ah)A) 49,3 % of rats developed cystic keratinizing squamous cell carcinomas. (Abstract truncated)