Peripheral odontogenic myxoma of maxillary gingiva: A rare clinical entity.

Odontogenic myxoma comprises 3-6% of all odontogenic tumors. Odontogenic myxomas are relatively rare benign mesenchymal tumors found exclusively in the tooth-bearing areas of the jaw and are usually located centrally in the mandible. Soft-tissue localization is rarely seen and is classified as peripheral myxoma. Peripheral myxoma is slow growing and less aggressive, as compared to the central myxoma. It has a low recurrence rate. Till date, only few cases of maxillary gingival myxomas are reported in the literature. Here, we present an unusual case of primary peripheral odontogenic myxoma occurring in the gingiva of anterior maxilla in a 41-year-old female patient.

INTRODUCTION

Peripheral odontogenic tumors demonstrate histological characteristics of their intraosseous counterparts, but occur solely in the soft tissue covering the tooth-bearing portion of the mandible and maxilla. These lesions are also known as extraosseous odontogenic tumors, soft-tissue odontogenic tumors, or odontogenic tumors of the gingiva.[1]

Odontogenic myxoma (OM) is a rare, benign odontogenic mesenchymal tumor arising from the embryonic connective tissue associated with the tooth-forming apparatus.[2] It was first described by Rudolf Virchow as myxofibroma in 1863 and was later renamed as odontogenic myxoma by Thoma and Goldman in 1947.[34] OM appears to originate from the dental papilla, follicle, or periodontal ligament. 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 odontogenic epithelium.[5]

It is a slow-growing but locally invasive neoplasm, usually occurring in the second or third decade of life. The occurrence of OM in the maxilla is rare as compared to the mandible and most reports show a slight predilection for females.[6] OMs are central lesions occurring in the jaw bones, commonly present as a painless swelling. Pain, displacement of teeth, and paresthesia are uncommon, thus the lesion can reach considerable size before the patient becomes aware of its presence and seeks treatment.[57]

Histologically, the tumor closely resembles the mesenchymal portion of a developing tooth. The tumor is not encapsulated and is composed of haphazardly arranged stellate, spindle-shaped, and round cells in an abundant loose myxoid stroma that contains only a few collagen fibrils. Small islands of odontogenic epithelium can also be found scattered in the stroma.[8] The treatment of this lesion involves surgical enucleation and curettage, which are the favored techniques. Because of its infiltrative character, this lesion is difficult to be curetted and this explains its high recurrence rate.[9] Cryotherapy as an adjunct procedure to curettage can be used to minimize the risk of recurrence.[10]

Intraoral soft-tissue myxoma is an extremely rare lesion and only few reports are available in the literature. In this article, a rare case of peripheral myxoma of anterior maxilla in a 41-year-old female patient is reported with emphasis on review of relevant literature.

CASE REPORT

A 41-year-old female patient was referred to our department with history of a slowly enlarging gingival mass in the anterior maxilla of 6 months duration. There was no associated history of trauma, pain, or tooth extraction. Intraoral examination revealed a solitary, non-tender swelling on the labial gingiva of the left maxilla in relation to 21 and 22, measuring about 1 × 2 cm [Figure 1]. The lesion was firm in consistency and the mucosa covering the lesion was normal in color; no mobility of the regional teeth was seen. The rest of the clinical head and neck examination was unremarkable. No radiographic changes were seen associated with the lesion [Figure 2]. Based on the overall findings, provisional diagnosis of fibroma was made.

Figure 1

Intraoral photograph showing the lesion on labial gingiva of left maxilla

Figure 2

Radiograph showing no bony changes

The lesion was surgically excised under local anesthesia and subjected to histological examination. Microscopic examination of Hematoxylin and Eosin stained section demonstrated atrophic, parakeratinized stratified squamous surface epithelium [Figure 3]. Underlying stroma showed abundant loose myxoid tissue containing few collagen fibrils. The tumor was composed of loosely arranged spindle- and stellate-shaped fibroblasts with small round nuclei suspended in a delicate network of collagen fibrils [Figures 4 and 5]. Small blood vessels were also present and no noticeable odontogenic islands were seen. A diagnosis of peripheral OM was made. Six months of follow-up showed no evidence of recurrence.

Figure 3

Hematoxylin and eosin stained section showing atrophic, parakeratinized stratified squamous surface epithelium (×10)

Figure 4

Loosely arranged spindle-and stellate-shaped fibroblasts with small round nuclei (×20)

Figure 5

Stellate-shaped fibroblasts in loose myxoid stroma (×40)

DISCUSSION

OM is a mesenchymal lesion that mimics microscopically the dental pulp or follicular connective tissue.[11] It is a rare, benign neoplasm that may be infiltrative and aggressive. The origin of OM is believed to be from the mesenchyme of a developing tooth or the periodontal ligament.[11] Some authors had previously associated its origin with a myxomatous change of an odontogenic fibroma or residual foci of embryonic tissue.[4] Based on the information gathered from the available literature, it is still somewhat arguable whether OM is truly an odontogenic neoplasm. However, its histological similarity to the stellate reticulum of a developing tooth, its exclusive occurrence in close proximity to the tooth-bearing parts of the jaws, the occasional association with a missing or an unerupted tooth, the presence of odontogenic epithelium in a minority of cases, and the fact that it rarely appears in other parts of the skeleton offer support to an odontogenic origin.[12]

The prevalence of myxoma is between 0.04% and 3.7%.[6] Most of the patients reported were young adults with average age ranging from 22.7 to 36.9 years. It is rarely seen in patients younger than 10 years of age and in adults above the age of 50.[13] A marked female predilection has been reported in several studies.[14] Mandible appears to be more affected than the maxilla, in the ratio of 2.5:1. In both jaws, the posterior region was most often affected.[12] But our case showed involvement of maxillary anterior region. OMs commonly occur centrally within the bone of the jaws, whereas our case was located peripherally on the gingiva. Buchner et al. analyzed one of the largest series of odontogenic tumors reported from one source and not even a single case of peripheral myxoma of maxillary gingiva was reported by them.[1]

Cases of maxillary peripheral OM of maxillary gingiva have been reported in the literature by Perrotti et al.,[15] Ramaraj et al.,[16] Aytac-Yazicioglu et al.,[17] Nazarov et al.,[18] and Raubenheimer et al.[19] Out of these six cases, only two cases were reported in the anterior maxillary gingiva.

OM is commonly reported as a slow-growing tumor that is generally asymptomatic, although some patients experience progressive pain in lesions involving maxilla and maxillary sinus, with eventual neurological disturbances. Central myxomas of the jaw have a tendency for extensive bone destruction, invasion into surrounding structures, and a relatively high recurrence rate; however, metastasis is rare.[20] Our case of soft-tissue myxoma was slow growing and localized in nature, with no evidence of recurrence or metastasis.

These tumors usually show variable radiographic features ranging from small unilocular lesions to large multilocular lesions, which often displace the teeth or resorb the roots. Various descriptions given for the multilocular pattern are “honeycomb,” “soap bubble,” “tennis racket,” “wispy,” and “spider-web” appearance.[21] Since our case was peripherally located in the gingiva, it showed no radiographic changes.

Histologically, this tumor resembles the mesenchymal portion of a tooth in development. The lesion is not encapsulated and is characterized by a proliferation of few rounded cells, fusiform cells, and star cells in an abundant myxomatous stroma with few collagen fibers. Small islands of odontogenic epithelial tissue can occasionally be found scattered in such a stroma.[22] OM has to be differentiated from other jaw tumors showing myxoid degeneration, such as myxoid neurofibroma, myxoid liposarcoma, and chondromyxoid fibroma. Chondromyxoid fibroma shows areas of cartilaginous differentiation, whereas myxoid neurofibromas tend to have scattered lesional cells that are S-100 positive. Myxoid liposarcoma is characterized by monomorphic fusiform cells in a mucoid stroma.[823]

Immunohistochemically, cells of OMs stain positively for transferrin, ferritin, alpha-l-antichymotrypsin, alpha-l-antitrypsin, S-100 protein, and vimentin; however, neuron-specific enolase, S-100 alpha and beta subunits, Factor VIII-related antigen, and cytokeratin are negative. The myxomatous matrix shows negative reaction for all the antibodies used. These results have confirmed that OM is a tumor of a dual fibroblastic–histiocytic origin and also suggests that the cells comprising OM are of myofibroblastic origin.[24]

OMs are treated surgically as they are radio-resistant tumors.[25] The lack of capsule and its infiltrative growth pattern are responsible for high rate of recurrence when conservative enucleation and curettage are performed.[12] OMs show a locally aggressive behavior and high recurrence and, hence, call for radical resection. However, soft-tissue myxoma is not reported to cause recurrence or metastasis;[26] hence, carefully planned conservative treatment or semi-radical approach is justified in these cases. In the present case, the tumor was completely removed by local surgical excision and there was no recurrence 6 months after surgery.