The respiratory epithelium. IV. Histogenesis of epidermoid metaplasia and carcinoma in situ in the hamster
Becci, P.J.; McDowell, E.M.; Trump, B.F.
Journal of the National Cancer Institute 61(2): 577-586
1978
ISSN/ISBN: 0027-8874 PMID: 355652 Document Number: 126567
The histogenesis of epidermoid metaplasia and carcinoma in situ was studied in female hamster tracheobronchial epithelium during and after 15 weekly intratracheal instillations of a benzopyrene-ferric oxide (BP-Fe2O3) mixture in saline. Within 24 h after the 1st instillation of BP-Fe2O3, goblet cell hyperplasia occurred. Mitoses were observed in small mucous granule cells (SMGC). SMGC probably represent mature mucous cells at early stages of their secretory cycle. Ciliated cells were extruded, and by 1 wk after the 1st instillation the epithelium was repopulated with mucous cells. During 1-5 wk the mucosubstances in these cells became more acidic, and the epithelium was composed of more than 1 cuboidal mucous cell layer. At 1 wk after the 5th carcinogen instillation, the epithelium was composed of basal cells and metaplastic cuboidal and flattened surface mucous cells (epidermoid metaplasia). Extensive keratinization occurred at 10 wk (cornifying epidermoid metaplasia). The luminal cornifying epidermoid cells contained periodic acid-Schiff positive, diastase-resistant mucosubstances. Localized areas of marked atypical metaplasia and carcinoma in situ were observed 20-50 wk after the 1st instillation. They were characterized by 1-2 layers of basal cells and 5-10 layers of pleomorphic cuboidal cells. The surface cells had all the characteristics of mucous cells, and cells near the basal lamina showed features of epidermoid cells. Mucus-filled intraepithelial cysts were observed. These data support the hypothesis of conversion of mucous cells to metaplastic and neoplastic cells.