Odontogenic myxoma presenting as localized inflammatory gingival enlargement: A diagnostic dilemma.

Odontogenic myxoma (OM) is a rare and locally invasive benign neoplasm found exclusively in the maxillofacial region. The radiographic and clinical features are variable, and the diagnosis is therefore not easy. A case of OM of the maxilla is described in a 19-year-old female, previously diagnosed as inflammatory gingival enlargement. Clinical, histological, radiographic, and computed tomographic (CT) scan assessments were done, which were confirmatory for OM. Surgical excision of the lesion was done. The patient was put on periodic recall, as the recurrence rate of the lesion was high. The biological spectrum of OM was highly variable and diagnosis at an early stage was very difficult. Gingival enlargement presentation might not always be an inflammatory reaction. All possible differential diagnosis should be explored and various diagnostic tools utilized, to screen the enlargement.

INTRODUCTION

According to the World Health Organization (WHO), Odontogenic Myxoma is classified as an odontogenic tumor of the ectomesenchymal origin. It appears to originate from the dental papilla, follicle, or periodontal ligament.[1]

Odontogenic Myxoma of the bone is a rare, benign tumor of unknown etiology. Most commonly, it occurs in the second and third decades. The mandible is involved more frequently than the maxilla, and most reports show a slight predilection for females.[2] OM is usually painless and displacement of teeth and paresthesia are uncommon clinical features. Therefore, it reaches considerable size before being detected, and perforation of the cortices of the involved bone may be seen.[3]

The evidence for its odontogenic origin arises from its almost exclusive location in the tooth-bearing areas of the jaws, its occasional association with missing or unerupted teeth, and the presence of an odontogenic epithelium.

Radiographically, the tumor presents as a unilocular or multilocular radiolucent lesion with well-defined borders and fine, bony trabeculae within its interior structure expressing a ‘honeycombed,’ ‘soap bubble,’ or ‘tennis racket’ appearance. Unilocular appearance may be seen more commonly in children and in the anterior part of the jaws.[4] Displacement of teeth is a relatively common finding, root resorption is rarely seen and the tumor is often scalloped between the roots.[5]

Application of a computed tomography (CT) Scan allows the production of panaromic, radial and axial 2D reconstruction. The extent of the lesion's relationship to teeth, root resorption, internal structure, cortical expansion and erosion, the boundary of the lesion and the presence of multiple lesions can all be evaluated.

Microscopically, the tumor consists of rounded, spindled, and stellate cells arranged in loose, myxoid stroma, with few collagen fibrils. Small islands of apparently inactive epithelial odontogenic rests may be scattered through the myxoid stroma.[6]

The recommended therapy varies from curettage to radical excision. Complete surgical excision can be difficult as the lesion is not encapsulated and the myxomatous tissue infiltrates the adjacent osseous tissue. This also accounts for the high recurrence rate of myxomas, which range from 10 - 30% with an average of 25%.[7]

CASE REPORT

A 19-year-old patient reported to the Outpatient Department of the Department of Periodontics, Faculty of Dental Sciences, Chatrapati Sahuji Maharaj Medical University (Erstwhile King George's Medical College), Lucknow, with a complaint of swelling in the left upper jaw region since one year.

Her history revealed exfoliation of a deciduous tooth in that area at the age of 12 years. Two months after exfoliation, the patient noticed a white mass in the canine premolar area, which resembled a nodule. One year back, the patient observed reddening of the nodule with a sudden increase in its size. The patient's records revealed that five months prior she had an incisional biopsy for the growth, which was diagnosed as chronic inflammatory enlargement.

Extraoral examination revealed no facial asymmetry. Intraoral examination revealed a diffuse erythematous swelling in between the left maxillary canine and first premolar [Figures 1 and 2]. The swelling measured 2.6 cm anteroposteriorly, 4.2 cm buccopalatally, and extended to the occlusal level superoinferiorly.

Figure 1

Preoperative swelling ― Buccal view

Figure 2

Preoperative swelling ― Palatal view

On palpation, the swelling was firm in consistency and tender. The overlying mucosa was immovably attached to the underlying bone.

The intraoral periapical, panoramic, and occlusal radiographs revealed a multilocular lesion with diffuse radio-opacity [Figure 3].

Figure 3

Intraoral periapical view of the swelling

As the radiographs were non-diagnostic, Dentascan was done for further clarification. ACT scan revealed multilocular radiolucency along with slight cortical expansion and cortical perforation [Figures 4–6].

Figure 4

Computed tomographic scan showing multilocular radiolucency in between 23 and 24

Figure 6

Multilocular radiolucency seen in three sections of the computed tomographic scan

Cortical expansion and perforation seen

After thorough scaling and root planing of the adjoining teeth, the patient was scheduled for excisional biopsy. Complete excision of the swelling along with slight osseous resection was done extending well beyond the swelling margin [Figure 7].

Figure 7

Immediate post excision

The histopathological examination revealed fragments of a myxomatous tissue [Figures 8 and [9]. The myxomatous tissue was even found infiltrating the osseous tissue, suggestive of a fibro-osseous lesion. Small islands of odontogenic epithelium were diagnostic of OM.

Figure 8

Highly cellular myxomatous tissue (H and E, 10×)

Figure 9

Myxomatous tissue infiltrating osseous lamellae (H and E, 40×)

Collaborating the clinical, radiological, and histological findings, the diagnosis was confirmed as odontogenic myxoma.

The patient has been put on a periodic recall program every month and recurrence has not been observed in the last six months [Figures 10–12]. The patient is to be recalled every six months thereafter.

Figure 10

One week post operation

Figure 12

Postoperative buccal view at six months

Postoperative palatal view at six months

DISCUSSION

Odontogenic myxoma is a rare tumor of the bone, and almost exclusively of the jaws, comprising of around 3 - 6% of all odontogenic tumors.[8] OM is found to occur most commonly in young patients with a predilection for females. The tumor is more common in the posterior parts of the mandibular jaw. The present case reports the tumor in the anterior part of maxilla. Although not very common, cases in the anterior maxilla are also seen.

Incisional biopsy of the patient was suggestive of a chronic inflammatory lesion. In all probability a superficial biopsy from the tumor margin may have resulted in a false conclusion.

Panoramic and occlusal radiographs were not very diagnostic. As is reported in the literature, the tumor presents a variable radiographic picture. The typical soap bubble or tennis racket appearance is not always seen. Zhang et al.[9] examined 41 cases of OM and found that on conventional radiographs, odontogenic myxomas presented varying radiographic appearances, which could be divided into six types as follows: Type I—unilocular; Type II—multilocular (including honeycomb, soap bubble, and tennis racquet patterns); Type III—involvement of local alveolar bone; Type IV—involvement of the maxillary sinus; Type V—osteolytic destruction, and Type VI—a mix of osteolytic destruction and osteogenesis. In the present case a type VI mixed picture of radiolucency and radio-opacity was visible.

Radiographically, a number of lesions resemble OM and should be differentially diagnosed from ameloblastoma, intraosseous hemangioma, aneurysmal bone cyst, central giant cell granuloma, metastatic tumor, and in some cases,of unilocular lesions, simple cysts.

For further clarification, a CT scan of the maxillary jaw was done. Mac Donald—Jankowski[10] compared the radiographic aspects of OM in conventional radiographs with Computed Tomography. The CT revealed bony cortices and its perforations with greater clarity.

Microscopically, spindle and stellate fibroblasts are associated with a basophilic ground substance and myxomatous tissue. It is a benign neoplasm without encapsulation. A spectrum of fibrous connective tissue stroma is present: from myxoid to densely hyalinized and from relatively acellular to cellular.

The lack of a capsule and infiltrative growth pattern is responsible for a high rate of recurrence when conservative enucleation and curettage are performed[1112]

Complete surgical excision of the lesion was performed. Periodic recall visits for the patient are planned, as the recurrence rate of the lesion is high.[7] Radical excision of the maxilla would be required if recurrence is noted.

To conclude, the odontogenic myxoma may present variable features on radiographs and superficial biopsies may be misleading. Due to the scarcity of studies using MR imaging, the characteristics of the myxoma have not been established satisfactorily. Therefore, additional studies are necessary to improve the diagnosis of this lesion, using the new imaging techniques that are now available to image this pathology.

An innocuous gingival enlargement presentation may sometimes be a disguise for a more serious pathology. Thorough exploration of the swelling and utilization of the available diagnostic tools may help screen such pathologies.