This article reviews odontogenic and developmental oral lesions encountered in the gnathic region of pediatric patients. The process of odontogenesis is discussed as it is essential to understanding the pathogenesis of odontogenic tumors. The clinical presentation, microscopic features, and prognosis are addressed for odontogenic lesions in the neonate (dental lamina cysts/gingival cysts of the newborn, congenital (granular cell) epulis of the newborn, melanotic neuroectodermal tumor, choristoma/heterotopia, cysts of foregut origin), lesions associated with unerupted/erupting teeth (hyperplastic dental follicle, eruption cyst, dentigerous cyst, odontogenic keratocyst/keratocystic odonogenic tumor, buccal bifurcation cyst/inflammatory collateral cyst) and pediatric odontogenic hamartomas and tumors (odontoma, ameloblastic fibroma, ameloblastoma, adenomatoid odontogenic tumor, primordial odontogenic tumor). Pediatric odontogenic and developmental oral lesions range from common to rare, but familiarity with these entities is essential due to the varying management implications of these diagnoses.

Primordial odontogenic tumor (POT) is a recently designated benign mixed epithelial and mesenchymal odontogenic tumor and only sixteen cases have been reported worldwide till now. Here we report an another case of POT in a 14-year old boy who presented with an asymptomatic buccal enlargement in the right maxillary region for past 4-5 months. A well-defined, unilocular, radiolucent lesion with impacted teeth was observed radiographically. A detailed account of clinico-radiographical and histolological differential diagnoses along with an updated literature review has been presented.

Primordial odontogenic tumor (POT) is a newly classified, mixed epithelial and mesenchymal odontogenic tumor, with only 17 reported cases to date. Herein, we report a case of POT that occurred in the right maxilla of a 10-year-old boy and reveal unique features in comparison with those previously reported. Radiologically, the lesion presented as a well-defined, unilocular radiolucency with notable radiopaque foci on the periphery. Microscopically, the tumor was mainly composed of dental papilla-like myxoid fibrous connective tissue, largely surrounded by non-keratinized squamous epithelium with numerous calcified particles, and partly enclosed by inner enamel epithelium-like columnar cells and enamel organ-like structures accompanied with cuboidal and/or stellate reticulum-like cells. Immunohistochemically, the epithelium tested positive for cytokeratin 14 and 19. Moreover, amelogenin and ameloblastin, matrix proteins relating to enamel formation, were positive in the covering epithelium. The tumor was enucleated as a whole, and no recurrence was recorded thereafter. Although the presence of numerous calcified particles was unique, we diagnosed this lesion as POT based on the above-described features. Furthermore, we emphasize the importance of the differential diagnosis of POT and other odontogenic tumors that resemble corresponding tooth germ components.

Although odontogenic lesions have been extensively described and studied, anomalous, challenging cases occasionally come to the attention of the pathologist. Here, we report the clinical and microscopic characteristics of an unusual cystic lesion of odontogenic origin. A 16-year-old male presented with swelling and pain to palpation of the right mandible as well as numbness of the right lower lip. Radiographically, the corresponding lesion was well-defined and radiolucent with internal radiopaque foci. It extended from the right first premolar posteriorly, approaching the angle of the mandible, and involved the mandibular first molar which was impacted and displaced. The second and third right mandibular molars were also impacted and displaced. The patient was treated by excisional biopsy under general anesthesia. The histopathologic examination revealed the presence of multicystic areas lined by a thin, non-keratinizing squamous epithelium that resembled the epithelial lining of a dentigerous cyst. In continuity with the cystic lining, areas of myxoid tissue reminiscent of dental papilla were observed. The myxoid tissue formed structures that were surfaced by an epithelium comprising a basal layer of ameloblast-like cells with reverse polarity of the nuclei. Above the basilar cells, additional layers of epithelial cells composed a structure resembling the enamel organ. Subjacent to the basilar ameloblast-like cells, a condensation of mesenchymal cells with polarized nuclei opposite to the ameloblast-like cells was present. These mesenchymal cells resembled odontoblasts. In addition, numerous mineralized structures amongst the odontogenic epithelial tissue were present. To date, the patient remains well and without evidence of recurrence after 36 months of follow-up.

BACKGROUND: A primordial odontogenic tumor (POT) is a rare, benign, mixed epithelial and mesenchymal odontogenic tumor that has been included as a new entity in the latest World Health Organization (WHO) classification (2017). POT consists of dental papilla-like myxoid connective tissue covered with a delicate membrane of ameloblastic epithelium. Only 15 cases have been documented worldwide, and here, we report the sixteenth case and the first one of South Korea.
METHODS: An asymptomatic lesion was discovered as an incidental radiographic finding in a 10-year-old boy. The patient had no complaints about the lesion. Cone-beam computerized tomograms revealed a round cavity with a defined cortical border measuring approximately 5 × 5 × 5 mm in size. The lesion was a POT. The patient was treated with enucleation. The tumor showed no recurrence for one year.
CONCLUSIONS: This is the first report of POT in South Korea using the novel diagnosis of POT after it was recognized and defined in the latest WHO classification. This novel diagnosis will be useful for pathologists and clinicians in diagnosing and differentiating this new and rare disease from other odontogenic tumors.

Primordial odontogenic tumor (POT) is a benign mixed epithelial and mesenchymal odontogenic tumor included into the current World Health Organization (WHO) classification of Head and Neck tumours in 2017. As far as the authors have confirmed, only eight cases of this tumor have been reported so far. This paper reports a case of POT that occurred in the right mandible of a 5-year-old patient. Panoramic radiograph showed a well-defined homogeneous radiolucency displacing the unerupted second deciduous molar to the deep part of the mandible. Histopathologically, the tumor was composed of cell-rich mesenchymal tissue with myxoid areas, surrounded by columnar epithelium and non-keratinized cuboidal epithelium in the outer layers. The histopathological diagnosis was POT. The expression patterns of cytokeratins (CK) 14, 18, 19, vimentin and CD34 suggested that the grade of differentiation of the POT was approximately equivalent to that of normal primary tooth germ tissues in cap stage to late bell stage.

Primordial odontogenic tumor (POT) is a rare lesion in the jaw which has been included as a new entity of benign mixed epithelial and mesenchymal odontogenic tumour in the latest World Health Organization (WHO) classification (2017). Only seven cases have been reported. It typically occurs in the posterior mandible. We report an additional case of POT in the maxilla of an 8-year-old girl presenting with an asymptomatic buccal enlargement. A well-defined, unilocular, radiolucent lesion was observed radiographically. Histologically, the tumor was mostly composed of loose fibrous connective tissue resembling dental papilla and a single layer of columnar epithelium covering the periphery of the tumor. In part, cords or nests of epithelium were present in the mesenchyme close to the periphery. Nestin, a marker of odontogenic ectomesenchyme, was positive in the mesenchymal tumor cells. We finally diagnosed the lesion as POT considering the possibility of other odontogenic tumors like ameloblastic fibroma or developing odontoma as a differential diagnosis. The patient shows no recurrence after 16 months. This case is the first report from Japan using this novel diagnosis POT after it was recognized and defined in the latest WHO classification.