Differences in collagen fibres in the capsule walls of parakeratinized and orthokeratinized odontogenic cysts.

Epithelial-mesenchymal interactions are thought to play an important role in the pathogenesis of odontogenic lesions. Keratocystic odontogenic tumour (KCOT) is a benign cystic neoplasm with a characteristic parakeratinized epithelial lining, which differs histologically and behaviourally from the so-called orthokeratinized odontogenic cyst (OOC). The purpose of this study was to investigate the differences in collagen fibres within the fibrous tissue walls of KCOT and OOC. Formalin-fixed paraffin-embedded tissue samples from 15 cases of KCOT and 15 cases of OOC were collected. Paraffin sections were stained with picrosirius red and observed under a standard light microscope using optical polarization. Unicystic ameloblastoma (UA, 15 cases) and subcutaneous epidermoid cysts (EC, 15 cases) were included in the study for comparative purposes. Significant difference was detected between the polarization colours in the fibrous tissue walls of KCOT and OOC (P<0.05), whilst no significant differences were found between KCOT and UA and between OOC and EC (P>0.05). The stromal collagen fibres of KCOT were different from those of OOC, but similar to those of UA, which suggests that the stroma of KOCT may play an important role in determining the neoplastic behaviour of the lesion through epithelial-mesenchymal interaction.