3. Discussion
Gardner described POdF in comparison with central odontogenic fibroma
and histopathologically separated it into peripheral ossifying
fibroma.5 POdF is a rare odontogenic tumor with
gradual growth consisting of a hard, elastic, smooth gingival
mass.1,3,4
The onset age of POdF is 5 months to 84 years, and there is seemingly a
predominant peak in middle age, specifically, during patients’
forties.1,2,6,7 The most common sites to develop POdF
are known to be the anterior maxilla and mandible in adults, while some
reports show that POdF also occurs frequently in the mandibular canine
to premolar region.7,8 A total of 25 reports of POdF
occurring in patients younger than 19 have been published, of which, 12
reported POdF development in the mandible (Table
1).6,7,9–18 Among those, two cases, including the
present case, reported POdF occurring in the mandibular premolar region
of teenagers.10
Histopathologically, POdF is characterized by odontogenic epithelium
scattered to various degrees in the fibrous
substrate.3,5,7 Moreover, bone-like, dentin-like, or
cementum-like hard tissue formation is observed, and it is classified
into epithelium-poor or epithelium-rich type according to the degree of
content of the dentin epithelium.19 Regarding the hard
tissue inside the lesion, bone-like and cementum-like hard tissue
formation have a reported frequency of 28.3% and 15.2%,
respectively.6 In the present case, a region was
described histopathologically as rich in cellular components as well as
a mixture of small mass and cord-like epithelial components similar to
Marasse’s epithelial remnants and Hertwig epithelial sheath. Moreover,
bone-like calcification was observed in the deep areas of the tumor.
In this sense, there are so far only four reports of POdF with hard
tissue inside the lesion among teenagers.17 Although
few reports have been published on hard tissue formation in POdF, it has
been suggested that the odontogenic epithelium inside the lesion may
induce hard-tissue formation, which requires a lengthy time to develop
in teenagers.17 Thus, it has been speculated that the
frequency of calcification in POdF might be low.
Some reports of CK-positive cells in the odontogenic epithelium of POdF
exist.20 In the present case, CK19-positive epithelial
components resembled Marasse’s epithelial remnants and Hertwig
epithelial sheath.
POdF was hypothesized to originate from the periodontal ligament, tooth
sac, and dental papilla.17 Central odontogenic fibroma
originates from the periodontal ligament or tooth sac according to the
2005 World Health Organization classification, while other authors have
reported the possibility of periodontal ligament origin as
well.19 We considered periodontal ligament or tooth
sac as the origin of the tumor described here for the following reasons:
the tumor was observed during the tooth-replacement period, tumor growth
was observed from the neck of the adjacent tooth, fibroblast growth
around the tumor did not resemble that of dental papilla, and Marasse’s
epithelial remnants and Hertwig epithelial sheath-like cells were
observed.
The rate of POdF recurrence after surgery is reportedly
low.17,21 However, some studies have reported an early
recurrence rate of 50% (29/58 cases).2,22,23