A light and scanning electron microscope study of epithelial thickenings and rete ridges in the adult hamster cheek pouch.

Cheek pouches from 8 adult male BIO strain hamsters were removed; half of them were routinely processed for light microscopy. The epithelium and connective tissue of the remaining pouches were separated using EDTA. These tissues were routinely processed for scanning electron microscopy and their separated surfaces examined; after this, some were reprocessed for light microscopy. A total of 1200 sections were examined by light microscopy and of these, 414 had at least one area showing rete ridges. Scanning electron microscopy confirmed the presence of isolated areas of either single or multiple rete ridges on both the separated epithelial and connective tissue surfaces. The presence of isolated areas of rete ridge formation in normal adult hamster cheek pouch mucosa needs to be taken into account in studies on experimentally altered cheek pouches so that the ridges are not interpreted as being part of a pathological change.