[New aspects of the histogenesis of inverted papilloma. 2. Comparative studies].

Frontal sections through the developing nasal cavity and paranasal sinuses in embryos from 25 to 76 mm length were compared to histological findings in IP's. It can be demonstrated that the growth pattern of asymmetric dichotomia and adventive "buds" typical for the embryonal mucosa is apparent in the IP as well. The embryonic determination of the Schneiderian diaphragm - to form the nasal cavity and paranasal sinuses by means of asymmetric dichotomia and adventive "budding" - is thus held responsible for the clinical and histological behaviour of the IP. Desmosomes connecting the IP cells are demonstrated under the electron microscope. Finally, suggestions for surgical treatment modalities are made.