A peripheral giant cell granuloma with extensive osseous metaplasia or a hybrid peripheral giant cell granuloma-peripheral ossifying fibroma: a case report

Abstract

Introduction: Peripheral giant cell granuloma and peripheral ossifying fibroma are clinicopathologically distinct gingival lesions. Both are included in clinical differential diagnoses of common benign and reactive gingival epulides in humans. It is often impossible to make a clinical distinction between the two entities, thereby making definitive diagnosis dependent on histopathologic features. While our search of the English literature revealed several reports of peripheral giant cell granuloma with 'bone formation', we were unable to identify any reports of hybrid peripheral ossifying fibroma-peripheral giant cell granulomas.

Case presentation: We report a case of a 44-year-old Caucasian man presenting with a three-month history of swelling of his right posterior mandible, related to an area of previous dental implant restoration. A clinical examination revealed modest extraoral facial swelling of his right posterior mandible, while an intraoral examination showed a 45 × 25 × 15 mm sessile, lobular soft tissue mass of the right posterior mandibular gingiva. The mucosal covering of the lesion exhibited focal surface ulceration. A panoramic radiograph showed two implants at the vicinity of the lesion with no other significant findings. An excisional biopsy of the lesion followed by histopathologic examination of the biopsy specimen revealed salient and distinctive features of peripheral giant cell granuloma and of peripheral ossifying fibroma, estimated at near equal proportions. This raises the possibility of a hybrid odontogenic lesion.

Conclusion: The presentation of this lesion, with areas of peripheral giant cell granuloma along with a distinct area of extensive osseous formation and stroma reminiscent of a peripheral ossifying fibroma, justifies consideration of this as a possible hybrid lesion. Although the biologic behavior of a combined lesion is not anticipated to deviate significantly from that of either of the single entities, this case resurrects an enduring debate as to whether peripheral giant cell granuloma and peripheral ossifying fibroma are simply parts of a disease spectrum, or whether some of these lesions represent true hybrid lesions. It is therefore recommended that more cases with histopathologic features similar to the lesion in our case be reported in the literature to further elucidate the histogenesis of these lesions.

Figure 1

Clinical photograph of intraoral gingival soft tissue swelling in the area of the right lower mandibular molar teeth.

Figure 2

Panoramic radiograph of patient’s jaws. Shows no evidence of intra-bony pathology in association with the soft tissue lesion (arrow).

Figure 3

Histopathologic micrograph of combined peripheral ossifying fibroma and peripheral giant cell granuloma. Hematoxylin and eosin-stained sections showing PGCG and POsF areas of lesion at (A) 10× magnification and (B) 20× magnification. (C) Same staining predominantly showing the PGCG area and prominent aggregates of multinucleated giant cell reaction (*) at 40× magnification. (D) Same staining showing a predominantly POsF area (arrow) within the hybrid lesion at 40× magnification. POsF, peripheral ossifying fibroma; PGCG, peripheral giant cell granuloma.