An Odontogenic Myxofibroma Associated with an Unerupted third Molar of the Mandible: A Case Report

INTRODUCTION

The odontogenic myxofibroma is a mixed type of myxoma which in a pure form is an extremely rare tumor¹ . It is a benign tumor arising from embryonic connective tissue associated with tooth formation¹ . Although myxomatous tumors arising in the jaws have been classified as belonging to the osteogenic and odontogenic origin types, a majority of these lesions seem to be of odontogenic origin because myxofibroma hardly occurs in any other bones of the skeleton outside the jawbones^2,3,4,5 . Virchow (1863) was probably the first to 6 describe the histological features of the myxofibroma . In 1947, Thoma and Goldman described Fibromyxomas of the jaws in detail¹ .

The odontogenic myxofibroma is non-encapsulated, benign mesenchymal tumor of 'stellate' cells within a mucoid ground substance. It is a well-established pathological entity and has been classified as a benign mesenchymal odontogenic neoplasm by the World Health Organization owing to its origin from the mesenchymal portion of various tissu components which develop the tooth^{5, 7} . However, there is no evidence that these lesions uniquely arise from the odontogenic apparatus¹ . The most common clinical symptoms are facial asymmetry, expansion of alveolar crest and with or without pain. The classic roentgenographic feature is a typical honeycombed appearance but can be confused with other types of multilocular bone tumors. Hence diagnosis is difficult without a biopsy.

Recently, we encountered a case of myxofibroma associated with an incompletely developed and embedded mandibular third molar. The tumor was diagnosed incidentally upon routine histopathologic examination of the surgical specimen originating from pericoronal portion of the unerupted molar.

This paper presents the clinical course and histopathologic findings of the case and also concerns about possible incidence of mesenchymal lesions from dental tissues which emphasize the importance of curettage and routine histopathologic examination of curetted tissue following extraction of an embedded/impacted tooth.

CASE REPORT

A 14-year old girl reported to Navodaya dental college and hospital with a complaint of continuous pain in mandibular right second and third molar region since a month. The patient presented no significant medical history. General examination revealed no obvious facial asymmetry and her both TMJ appeared normal upon palpation. Upon intra oral examination, the patient had healthy full set of dentition excluding third molars. Tenderness was elicited over retromolar region distal to second molar. Radiographic examination confirmed presence of all third molar tooth buds. In right molar region the tooth bud was providing evidence of impingement on the distal root of second molar. An increased follicular space was noted at the occlusal surface of tooth bud (figure 1). Considering the increased force of eruption on right second molar as an etiologic factor for pain and its radiologic evidence to undergo impaction, the tooth bud was planned for abortion.

After obtaining the consent, surgical extraction of the tooth bud was performed under local anesthesia. Following the tooth extraction, we noticed a tissue resembling hyperplastic dental follicle in the alveolar socket. All the tissue was excised carefully and bony socket was curetted. The excised tissue was submitted for histopathologic examination.

On microscopic examination the H&E stain (figure 2 &3) revealed stellate and spindle shaped mesenchymal cells embedded in a loose myxoid / mucoid matrix. Many areas exhibited variable amounts of mature collagen interspersed within the myxoid component. No odontogenic epithelial remnants were seen. All these features were suggestive of odontogenic myxofibroma.

Sometimes, it is difficult to differentiate hyperplastic dental follicle from odontogenic myxofibroma and odontogenic fibroma. To rule out the bias and confirm the diagnosis, we sent the specimen for a second opinion and also immunohistochemical staining was performed.

In immunohistochemical examination, the sections were stained with vimentin and S-100 protein to rule out any hyperplastic dental follicle. It showed stellate and spindleshaped cells which were stained diffusely with vimentin and S-100 protein did not take up the stain (figure 4, 5, 6 & 7). The positive vimentin and a negative S-100 protein strongly suggested a diagnosis of odontogenic myxofibroma. The second opinion was also in favor of odontogenic myxofibroma.

After confirming the diagnosis the patient was informed and was followed for two years. During the course of follow up no recurrence of the lesion was noted (figure 8).

DISCUSSION

Most central myxomatous tumors of jaws are not discovered until these lesions have developed to a progressively advanced stage, inducing the various clinical symptoms such as asymmetry of the face, spontaneous pain and abnormal sensations² . As the tumor is frequently associated with missing, unerupted, or partially formed teeth¹, it is often confused with hyperplastic dental follicle. The close histological similarity of the immature/hyperplastic pericoronal tissues to tumour demands a histopathologic as well as an immunohisto chemical analysis of the specimen in order to distinguish tumour from innocuous dental tissues.

However, we encountered an asymptomatic odontogenic myxofibroma originating from pericoronal tissues of an embedded, partially developed tooth at a relatively very early stage which was confirmed by both histopathologic and immunohistochemical examination. After diagnosing, we followed the case for two years and to monitor any recurrence. There were no signs of recurrence after two years which justified our treatment plan of close monitoring by regular follow up after curettage and avoiding any further surgical interventions after the diagnosis.

There is a paucity of literature reporting odontogenic myxofibroma arising from an impacted or embedded tooth. 

However a review of the literature has produced 213 adequately documented examples of myxofibroma of the jaws, including 91 from the maxilla and 132 from the mandible⁶. As per our knowledge, this may a second most case of odontogenic myxofibroma which was diagnosed incidentally around an mandibular impacted third molar.

CONCLUSION

This case report emphasizes the importance of thorough curettage of dental tissues following removal of impacted teeth and subsequent microscopic examination of suspicious tissues to rule out any tumour or pathology. Hence, oral surgeons and surgical pathologists are cautioned against the benign neglect and misinterpretation of such immature dental tissues which in most of such instances successfully prevent the progression of the lesion and unnecessary surgical intervention.