Primordial Odontogenic Tumour: Clinico-Pathologic Analysis of Six Cases of a Previously Undescribed Entity

Aim: To describe the clinicopathological and immuno-histochemical features of six tumours that do notfulfil the criteria of any of the currently classifiedodontogenic tumours.Methods and results: The patients were three malesand three females, whose ages ranged from 3 yearsto 18 years (mean, 11.5 years). In all cases therewere well-defined radiolucencies associated with une-rupted teeth apparently showing a pericoronal rela-tionship. Microscopically, all tumours were composedof variably cellular loose fibrous tissue with areassimilar to dental papilla, entirely surrounded bycuboidal to columnar epithelium resembling theinternal epithelium of the enamel organ. Mesenchy-mal tissue was positive only for vimentin, and Ki67expression was very low (<2%). The epithelium waspositive for CK AE1/AE3, CK5, CK14, and CK19, butnegative for CK18 and CK20. All cases showed cleardemarcation from the surrounding bone, and weresurgically removed, with no recurrences after follow-up ranging from 6 months to 20 years.Conclusions: These findings differ from thoseobserved in other odontogenic lesions, such as ame-loblastic fibroma, odontogenic myxoma, odontogenicfibroma, and hyperplastic dental follicles. The termprimordial odontogenic tumour is proposed todescribe this novel lesion.Keywords: dental follicle, dental papilla, jaws, odontogenic tumour, tooth primordium