The patient is a 37-year old woman who presented with a soft tissue growth on her right maxillary gingiva. Intraoral examination revealed a painless rubbery mass on the palatal aspect of the maxilla. An excisional biopsy was performed.
Histological sections reveal squamous mucosa with a partially ulcerated spindle cell proliferation. The tumor is comprised of monotonous spindle cells with interposed granulation tissue and a few epithelial odontogenic rests toward the base of the spindle cell component. Focally, there was evidence of osteoid and amorphous eosinophilic calcified material. By immunohistochemistry, the lesional cells are negative for smooth muscle actin (SMA), S-100, cytokeratin (AE1/AE3), Melan-A, CD34 and HHV-8.
Ossifying fibroma is a rare benign bone-producing fibrous neoplasm of the skeleton. According to the 2005 World Health Organization Classification of Tumours, ossifying fibroma of the craniofacial skeleton are separated into those of odontogenenic origin (i.e. cemento-ossifying fibroma) and a juvenile type, further subdivided into trabecular and psammomatoid juvenile ossifying fibromas.
Peripheral ossifying fibroma (POF) is rather a reactive and not a neoplastic lesion. The possible inciting triggers for its development include dental plaque, stones and/or appliances. Both ossifying fibroma and peripheral ossifying fibroma are believed to originate from the periodontal ligament and therefore, are cement-, or bone-producing. POF has also been termed peripheral odontogenic fibroma with cementogenesis, peripheral fibroma with osteogenesis, peripheral fibroma with calcification, fibrous epulis, and calcifying fibroblastic granuloma, among others.
POF most commonly arises on the soft tissue of the gingiva. It is usually small, occurs on anterior maxilla, and affects young women in the second or third decade of life, such as this patient. The ulcerated lesions, as in this case, are more likely to be painful and causes the patient seek care sooner. Rare multicentric variant has been described.
Differential diagnosis of a gingival lesion that may have a similar clinical presentation is broad and includes lesions such as pyogenic granuloma, fibrous epulis, fibroma, peripheral giant cell granuloma, and calcifying odontogenic cyst. Imaging may identify the calcified elements within the lesion; however they become prominent only if the lesion is long-standing.
Histologically, peripheral ossifying fibroma is comprised predominantly of plump proliferating fibroblasts, granulation tissue and lymphoplasmacytic infiltrate. In its deeper aspect, the fibroblastic matrix tends to become more collagenized, and the inflammatory infiltrate is less pronounced. Osteogenesis is a key for diagnosis and may take a form of osteoid, immature or lamellated bone, dystrophilc calciphilications and cementum-like material. It is usually easier to identify in the subepithelial zone, or in the portion of the lesion beneath the ulceration.
While it is a reactive gingival proliferation, POF may have significant consequences if not treated promptly. Its growth may cause bone erosion, displacement and loss of both bone and teeth. It has been shown to have a high recurrence rate that is quoted from 7% up to 45% in the literature.
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