A nine year old paediatric patient, with no clinical history of interest, was referred to the paediatric maxillofacial surgery unit for presenting dental inclusion. The radiological study showed an inclusion of the lower left canine, with a radiolucent area around 33, and she was admitted for surgical correction, with a preoperative diagnosis of follicular cyst. The surgical treatment carried out consisted of the removal of the "follicular cyst" with curettage of the bone cavity and extraction of the included canine, with subsequent filling with "Bio-oss" bone, the post-surgical evolution being satisfactory.
The surgical specimen obtained through curettage comprised several irregular fragments of greyish colour and low consistency that together measured 0.8 x 0.7 cms and a canine (0.9 x 0.5 cms) resulting from the exodontia. The histological study showed an unaltered tooth structure, accompanied by fragments of fibrous tissue inside which there were numerous solid nests of odontogenic epithelial elements arranged in compact micronodular formations with a swirling cellular arrangement. The elements forming these structures were basaloid in morphology, with monomorphous, oval or fusiform nuclei, somewhat hyperchromatic, although without evidence of divisional activity. Mixed with these structures were glanduliform formations, sometimes tubular in appearance, with a lining of cylindrical, homogeneous cells and nuclei often polarised towards their base. At intercellular level and in a scattered manner, small calcified basophilic spherules appeared as well as areas of irregular contour of amorphous and hyaline deposit, PAS + diastase resistant, positive to Congo Red although green refringence to polarised light was not observed. In view of these data, a diagnosis of follicular adenomatoid odontogenic tumour associated with retention of the canine dental structure was made.

From the resected soft tissue material, an immunohistochemical study was carried out, which firstly showed a reactivity of the proliferating elements, both in the nodular and adenomatoid areas, against the AE1-3 keratin cocktail. Nuclear positivity for the p63 protein (a marker of basal or progenitor cells) was also observed, this nuclear reactivity being present in both the glanduliform areas and in the swirling nests of spindle cells.

The proliferation marker Ki-67 marks only 2-3% of the constituent cells of the tumour lesion, with positivity often appearing in clusters of spindle cell nodules. Detection of the melanin differentiation markers HMB45 and Melan-A was negative as was detection of the hormone receptors oestrogen (ER) and progesterone (PRg) and beta-2-microglobulin.