A typical Odontogenic Neoplasm: Peripheral Odontogenic Fibroma

INTRODUCTION

Odontogenic tumours are lesions derived from epithelial, ectomesenchymal and/or mesenchymal elements that still are, or have been, part of the tooth forming apparatus. WHO classified odontogenic tumours firstly on a lesion’s behavior as benign, malignant and non-neoplastic and further subdivided based on the types of odontogenic tissues involved. As per World Health Organization (WHO), odontogenic fibroma falls into the category of mesenchyme and/or odontogenic ectomesenchyme with or without odontogenic epithelium.1

The odontogenic fibroma (OF) is a rare neoplasm characterized by varying amounts of inactivelooking odontogenic epithelium embedded in a mature, fibrous stroma.1 Odontogenic fibromas can be topographically distinguished into two diverse forms: the intraosseous or central odontogenic fibroma (COF) and the extraosseous or peripheral odontogenic fibroma (POdF).2 Histologic typing of POdF is considered as a soft tissue mucosal counterpart of COFand is one of the hard ones to pin down because of its rarity and improbability of the number of discrete types that have evolved. WHO has reported POdF as a relatively exceptional benign odontogenic neoplasm and the third most common odontogenic tumor.3

Clinically it can be misidentified as the frequently occurring exophytic gingival lesion- like the pyogenic granuloma or fibrous hyperplasia.4

Case report

A 16-year-old female patient checked-in to the Department of Periodontics in the month of March 2012 complaining of a painless swelling in her upper front tooth region. She described that the lesion had been developing from the past 5 months. Initially, the lesion was smaller in size, which then progressed to attain its present dimension of 0.5×1cm.

Clinically, interdental area of maxillary teeth #11, #12 showed a single, lobulated, erythematous, sessile swelling causing displacement of permanent central and lateral incisor (figure 1a, 1b). Bone sounding under local anesthesia on the palatally enlarged area showed probing depth of 8mm, indicating a soft tissue enlargement. No history of trauma and no relatable medical history were present. Examination of head and neck was unremarkable. Routine blood investigations were within normal limits. Radiographic evaluation revealed spacing and haziness between maxillary tooth # 11and #12 (figure 2). CT scan showed radiolucency encroaching about 3.46mm deep into the palatal bone (figure 3). Provisional diagnoses were assigned as peripheral ossifying fibroma, a benign odontogenic neoplasm.

After obtaining written informed consent from parents, incisonal biopsy was performed under local anesthesia as radiographic examination showed encroachment of lesion into bone. The specimen was sent for histopathological examination and the final diagnosis was confirmed as POdF. With incisonal biopsy, labial aspect of the lesion healed completely, leaving behind the enlargement only on the palatal aspect. After obtaining the biopsy report, the lesion was completely excised on the palatal side as well. The excised tissue was sent again for histopathological examination and the second biopsy report also confirmed diagnosis as POdF. Bony walls were enucleated and meticulous scaling and root planing was done (figure 4, 5, 6). To enhance healing, we decided to use autologous platelet rich fibrin (PRF) as a biological wound dressing. Resorbable 4-0 polyglactin 910 * sutures were placed and postoperative instructions were given (figure 7). Analgesics (combination of paracetamol 500mg and diclofenac sodium 50mg) was prescribed twice daily for three days and the patient was recalled after 15 days for further evaluation and removal of sutures. After 15days, the wound site showed newly formed granulation tissue (figure 8). At 31 days, the wound had completely healed and could not be differentiated from the surrounding tissue (figure 9). After 3-months, soft tissue showed resistance to probe penetration thus depicting formation of new connective tissue (figure 10a,10b). Periodical follow up of upto 2years showed satisfactory healing with diminution of space between #11, #12 (figure11a,11b).

Histopathological features: The submitted specimen was fixed in formalin, routinely processed and stained with hematoxylin and eosin (H&E) staining. Sections revealed a hyperplastic stratified squamous epithelium with an underlying dense fibrous connective tissue. Regions within the connective tissue showed the presence of cells arranged in the form of islands and strands. The cells within the islands had a dense eosinophilic cytoplasm and hyperchromatic nucleus which was placed away from the basement membrane. These features were consistent with inactive odontogenic epithelium (figure 12,13,14). The connective tissue also showed presence of blood vessels and moderate chronic inflammatory cells. On the basis of clinical, radiological and histological characteristic features our case was found to be similar to peripheral odontogenic fibromas documented in the literature.^5,6 The second biopsy report of complete surgical excision of the lesion also showed similar histological features confirming our final diagnosis as peripheral odontogenic fibroma (POdF).

DISCUSSION

Odontogenic tumors and tumor-like lesions make up a wide range of heterogeneous diseases, including hamartomatous or non-neoplastic tissue proliferations, benign neoplasms and malignant tumors with metastatic potential.1 POdF has been addressed with various synonyms like extraosseous odontogenic tumors, soft tissue odontogenic tumors and odontogenic tumors of gingiva.7 Even though POdF comprise only 0.05% of all biopsy specimens, it is the most common peripheral odontogenic tumour, even more than its central counterpart by a ratio of 1.4:1.⁷

The formation and development of the POdF is still not clear but derivation form each tissue component (dental lamina rests, ectomesenchyme, surface epithelium, periodontal ligament) resident to the site of occurrence has been speculated.⁵

Gardner analyzed the dilemma of the terminology needed to be used and proposed the use of adjectives ‘WHO type’ and ‘non WHO type’ to discriminate between the true fibroblastic odontogenic neoplasm and the reactive lesions.⁶ The POdF is a classically single, nondescript, rare, benign, unencapusalted, exophytic gingival mass of fibrous connective tissue, typically covered with unremarkable surface epithelium.⁸ Similar characteristics were observed in the present case. Sometimes the areas of calcification are seen radiographically.⁵ No calcification were observed in this case report but bone resorption was seen in the palatal area suggestive of peripheral cuffing.⁵ To correctly speculate the age range, site of occurrence, gender and race for POdF is difficult, because the data available are wide-ranged and inconsistent.³ The most common site is canine / premolar areaand incisor-cuspid area,3,6 both in the maxilla and in the mandible.² But our case report shows the presence of lesion in a young female patient with site predilection of interdental region of #11,#12 displacing the involved teeth.

In the present case to have a faster and better healing Choukron’s PRF was used as a surgical adjuvant. PRF is physiologic glue; therefore, the compression of it into a membrane provides a compact matrix.⁹ Neoangiogenesis and epithelial cell migration influenced by the concentrated growth factorscan be used to shield open wounds.10

The POdF must be histologically differentiated from reactive proliferatingperipheral ossifying fibroma;⁶ in our case, the characteristic histological features were similar to other reports in the literature.^5,7 Gardner suggested that the peripheral ossifying fibroma (POF) and WHO type POdF are two distinct lesions even though they share certain histologic features in common. While the WHO type POdF often exhibits extensive proliferation of odontogenic epithelium and dysplastic dentin formation which are found rarely in POF. Well formed bone and ulceration may be present in POF but it is only occasionally found in the WHO type POdF.One important distinguishing feature between the two lesions is their difference in their connective tissue components. POF is very cellular, consisting of closely packed fibroblasts whereas POdF lacks the pattern and shows cellular strands interwoven with relatively less cellular areas.⁶

Our case showed no recurrence after 2 years of follow up supporting the finding of Buchner et al8 but contradicting others.^3,5 Daley & Wysocki showed a significant recurrence rate of 38.9%³ whereas Ritwik& Brannon reported 50% of recurrence.⁵ Early identification of the lesion by using modern radiographic diagnostic innovations like CT scan over IOPA helped in avoiding further progression of lesion into the bone and also guided us in planning the complete excision of the lesion. However complete surgical excision sometimes results in a mucogingival defect. Hence, periodontal plastic surgery should be planned to correct these defects. The present case with 2 year follow up showed neither any mucogingival defect nor recurrence of the lesion. It was also observed that there was a diminution of space interdentally and also revealed a radiographic evidence of bone formation in between the involved teeth (figure 15).

*coated Vicryl plus, Ethicon Inc, New Delhi, India