Management of a rare case of peripheral squamous odontogenic tumor of the gingiva.

Odontogenic tumors (OTs) arising from the periodontium are quite rare. Squamous OT (SOT) is one such neoplasm which has an exceedingly rare occurrence. According to the literature, there have been very few reported cases of SOT with a very small percentage involving the gingiva. Most of the times, these tumors are located within the bone, only a very few peripheral cases been noted so far. Although predominantly benign, the possibility of a malignant transformation prevails. Our case describes a rare presentation of a peripheral SOT involving the upper anterior gingiva in a 59-year-old patient, which presented clinically as a firm and fibrotic swelling. An excisional biopsy was performed as a part of surgical management and for microscopic evaluation to confirm the clinical diagnosis. A soft tissue graft was harvested from an edentulous area to cover the deficit at the surgical site. The patient was evaluated at periodic intervals to assess the healing outcome and for any recurrence of the lesion.

INTRODUCTION

Odontogenic tumors (OTs) comprise a wide range of neoplasms. Although they are principally osseous in nature, some may exclusively involve only the soft tissues. Such kind of tumors arising from the periodontium are very rare, the majority of them being benign in nature.[1] Squamous OT (SOT) is one such lesion that was first described in 1975.[2] SOT is considered a rare, benign locally infiltrative, epithelial OT. Earlier this tumor had been reported under a variety of names including benign epithelial OT, acanthomatous ameloblastoma, acanthomatous ameloblastic fibroma, squamous metaplasia of residual odontogenic epithelium, and benign odontogenic tumor unclassified.[3]

It was earlier believed that SOT was a mere representation of an atypical acanthomatous ameloblastoma; however, it has now been accepted as a distinctive entity. The WHO histological typing of OTs has classified SOT as a benign tumor of odontogenic epithelium without an odontogenic ectomesenchyme. It is considered to arise as a result of neoplastic changes of the epithelial cell rests of Malassez (ERM).[4] SOT presents as a slow-growing painless expansive swelling that may or may not be associated with radiographic changes.

Clinicopathologically, three main types of SOT exist, the intraosseous, mural, and the extraosseous variants. However, clinically two main forms exist, central SOT and peripheral SOT (PSOT).

There is a paucity in the number of published cases of PSOT in literature, a case also been reported by the author previously.[5] This present report describes a rare case of PSOT.

CASE REPORT

A 59-year-old male patient reported with a painless swelling in relation to the left upper anterior gingiva for the past 2 years [Figure 1]. There was no relevant medical history. Intraorally, a firm diffuse swelling was seen on the labial aspect extending from the distal aspect of 22 to the mesial aspect of 24 (1.2 cm × 2.5 cm in size). The surface of the lesion was smooth and nonlobulated. The lesion extended up to the middle-third of the crown with a pseudopocket measuring 10 mm in relation to 23. On palpation, the lesion was firm, fibrotic, well–defined, and nontender. Radiographs did not reveal any changes [Figure 2]. Based on the above-mentioned findings, a provisional diagnosis of fibroma was made and a differential diagnosis of peripheral ossifying fibroma, peripheral giant cell granuloma were also considered.

Figure 1

Intraoral view showing a well-defined sessile growth extending from the distal aspect of maxillary left lateral incisor to the mesial aspect of maxillary left first premolar

Figure 2

Intraoral periapical radiograph

The treatment plan for all the above-mentioned lesions is excision of the lesion as a whole and histopathological examination for confirmation of the clinical diagnosis. The treatment plan included soft tissue grafting if required due to the size and extent of the lesion (22 distal to 25 mesial).[6]

Crevicular incisions were placed on the labial aspect extending from 21 to 25. Releasing incisions were placed on either side of the horizontal incisions. Following elevation of a full thickness mucoperiosteal flap [Figure 3], the lesion was excised completely [Figure 4] and transferred to 10% neutral buffered formalin.

Figure 3

Full thickness mucoperiosteal flap elevated and area curetted

Figure 4

Excised tissue

The excision of the tumor resulted in soft tissue deficiency at the surgical site [Figure 5]. A soft tissue graft was harvested from the edentulous area in relation to the right maxillary first molar region [Figure 6]. Before adaptation of the graft onto the defect site, the root surface was planed, and root conditioning was done using tetracycline. The graft was stabilized using a 5-0 vicryl suture [Figure 7] and covered with a periodontal dressing. The donor site was packed with a hemostatic agent (Ab gel) and sutured with a nonresorbable suture [Figure 8].

Figure 5

Surgical site after excision

Figure 6

Soft tissue graft harvested from edentulous area in relation to maxillary right first molar region

Figure 7

Graft placed on the defect area and secured using 5-0 vicryl suture

Figure 8

Donor site packed with hemostatic agent and secured with 3-0 black braided silk suture

The excised lesion was stained with hematoxylin and eosin for histopathological examination. Sections were prepared, and microscopic examination revealed peripheral stratified squamous epithelium. The underlying section showed islands and broad strands of well-differentiated squamous epithelial cells in a mature connective tissue (CT) stroma [Figure 9]. The islands were lined by flat to cuboidal cells and exhibited vacuolization, microcyst formation, and squamous differentiation [Figure 10]. Based on the above-mentioned findings, a final diagnosis of PSOT was given.

Figure 9

Histopathology under ×10 magnification depicting peripheral stratified squamous epithelium with islands of squamous epithelium in the CT

Figure 10

Histopathology under ×40 depicting squamous islands lined by cuboidal cells and presence of vacuolated cells

The patient was reviewed, and healing of both the donor and recipient sites was satisfactory with no signs of recurrence after 20 weeks of clinical assessment [Figure 11].

Figure 11

Twenty weeks postoperative view of the recipient site

DISCUSSION

The periodontium indeed is an unusual site for occurrence of tumors of odontogenic origin. SOT is a rare tumor that is believed to occur as a result of proliferation of ERM associated with alveolar process adjacent to lateral root surface of the teeth or the dental lamina. However, surface stratified squamous epithelium and rests of Serres have been cited as sources for extraosseous variants.[2]

To date, only 44 cases of SOT have been reported in the literature; however, the frequency of the occurrence of OTs cannot be precisely stated due to paucity of documented cases of SOT.

Although only a few reported cases, it is still possible to arrive at some conclusion pertaining to the demographic, clinical, as well as the radiographic presentation of such tumors. SOT has been found in patients in ages ranged from 8 to 74 years, the age of the patient in our case was 59 years. Males and females tend to be equally affected.[7] However, there is a slight male preponderance. There is no apparent predilection for occurrence in either the upper or lower jaw. However, the lesions involving the maxilla present more often in the anterior region, whereas mandibular cases are more often seen in the posterior region. Out of the reported cases on SOT, almost 50% of the cases occurred in the posterior region of the mandible. The tumor in this present case was seen in the maxillary anterior region. Maxillary lesions seem to grow more aggressively than the mandibular ones.[8] SOTs clinical and radiographic features are neither unique nor sufficient for diagnosis, as this tumor may be mistaken for a number of other pathologies. The radiographic findings in our case did not reveal any pathology.

SOT generally produces a readily recognizable pattern on histologic examination. Numerous islands of proliferative squamous epithelium were easily recognized, distinctly demarcated from the surrounding stroma by a flattened layer of cells at the periphery. Diagnosis is generally based on histopathologic findings of SOT to obviate possible misdiagnosis for a peripheral ameloblastoma[910] where a palisaded columnar ameloblastic cells lining the epithelial islands are seen with a stellate reticulum configuration of the central portion of the islands.

SOT varies in its aggressiveness; however, total resection is necessary in the most cases.[11] The surgical management involved a complete excision of the tumor and placement of a soft tissue graft to cover the soft tissue deficiency in the surgical area. Till date, <50 cases of SOT have been reported in the literature. Recurrence has been reported in only one case.[9]

Five months postoperatively, well integration of the graft was seen with no evidence of any recurrence. However, the patient was periodically monitored.

CONCLUSION

The characteristics of OTs generally depend on the cellular and molecular mechanisms associated with teeth development, bone metabolism, and malignant potential. Although rare, SOT has the propensity to transform into a malignant disorder such as an intraosseous squamous cell carcinoma. Hence, timely diagnosis and appropriate therapy are important.

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Conflicts of interest

There are no conflicts of interest.