3. Discussion and a Review of Literature
Myxomas are rare benign tumors of mesenchymal origin. They are locally invasive and occur in various tissues, including cardiac, skeletal, cutaneous, and subcutaneous tissue, aponeuroses, genitourinary tract, and skeletal muscles [15]. Odontogenic myxoma was initially named as “myxofibroma” by Rudolf Virchow in 1863 due to its histologic similarity to the mucinous substance present in the umbilical cord [16]. Later in 1947 it was renamed to “odontogenic myxoma” by Thomas and Goldman [17]. World Health Organization (WHO) defines this tumor as “a locally invasive neoplasm that consists of angular and rounded cells in mucoid background” [18].
It is the third most common odontogenic tumor after odontoma and ameloblastoma respectively and accounts for 3-6% of all odontogenic neoplasms [3]. It most frequently occurs in the second to fifth decade of life and the average age of occurrence ranges from 23 to 30 years [1,2]. Women are more commonly affected than men with a ratio of 1.5:1. The mandible is the more commonly affected than maxilla, with the posterior body, ramus and angle being the most common sites respectively [5]. Regardless of the jaw, odontogenic myxoma is usually found in relation to a tooth, typically a premolar or molar [7]. However, there has been a few case reports of a peripheral odontogenic myxoma occurring solely on the soft tissue [19,20]. In an updated analysis of 1692 cases by Chrcanovic et al. [21] approximately 75% of the lesions showed signs of cortical bone perforation, 62.9% of the lesions had a radiological multilocular appearance, and 34.7% of the lesions showed the presence of angular septa. Nearly 20% of the lesions presented root resorption of adjacent teeth and 53.8% of the cases showed tooth displacement and/or uneruption due to lesion’s growth. Only 6.8% of these lesions crossed the midline of the jaws which makes our case truly a rare entity.
Clinically, odontogenic myxoma is a painless, slow-growing, benign but locally aggressive lesion that displaces and/or resorbs its adjacent structures including teeth roots and cortical bone. This lesion can advance into paranasal sinuses and zygomatic process of the maxilla as well [5,16,22]. Unorthodox cases of rapidly expanding odontogenic myxoma of the jaw have been reported [23,24]. In many cases however, these lesions are coincidentally diagnosed during a routine dental checkup [7,25]. Some odontogenic myxomas are found to be associated with unerupted teeth [26]. Ulceration of the overlying mucosa is rarely seen and only occurs in case of the lesion being in the pathway of dental occlusion. Nevertheless, rapid growth and invasion of the soft tissue may occur as well [27]. Our case presented with consistent pain which was in contrast of typical clinical findings of odontogenic myxoma reported in the literature.
Radiographically, odontogenic myxoma’s appearance can vary from uniloculated to multiloculated and from completely radiolucent to mixed radiolucent-radiopaque [7,21,27,28]. Furthermore, the margins of this lesion have been variably described as corticated, non-corticated, poorly defined, and diffuse [11,16,22]. The multilocular appearance usually presents as “soap-bubble”, “honeycomb”, “tennis racket”, “spiderweb” or “wispy”. However, recently patterns resembling a “sun-ray” or “sun-burst” appearance have also been reported that may suggest a more destructive, expanding behavior of this lesion [1,2,11,22,29,30]. The lesion usually displaces and/or resorbs adjacent teeth roots [5,22]. In some cases, this lesion is found encapsulating an unerupted tooth [26]. Our case initially presented with uniloculated and small radiolucency which further developed to a multiloculated lesion with small septa extending into the lesion and giving it a tennis racket appearance which is consistent with typical findings of odontogenic myxoma.
Differential diagnosis based on radiographic findings differs depending on the loculation status of the lesion. For uniloculated lesions differential diagnosis includes but not limited to periapical cyst or granuloma, lateral periodontal cyst, simple bone cyst or unicystic ameloblastoma. For multiloculated lesions differential diagnosis include central giant-cell granuloma (CGCG), cherubism, multicystic ameloblastoma, intraosseous hemangioma, aneurysmal bone cyst, odontogenic keratocyst (OKC), metastatic tumor, and osteosarcoma [1,2,26,31,32].
Histologically, the bulk of odontogenic myxoma is made up of loosely arranged, spindle-shaped and stellate cells, many of which have long fibrillar processes that tend to intermesh with apparently inactive odontogenic epithelium scattered through the myxoid (mucous) ground substance. The loose stroma tissue is mainly made up of hyaluronic acid and chondroitin sulphate as in normal tissues, but excessive in amounts. The present cells in this stroma do not show evidence of significant neoplastic activity including pleomorphism, prominent nucleoli or mitotic figures. Growth pattern of this lesion is differentiated from other lesions by the fact that it gradually grows by secretion of ground substance rather than cellular proliferation. The gelatinous consistency of myxoma permits the lesion to permeate through bony trabeculation leaving no clear margin, therefore making its complete removal substantially difficult [1,2,3,26,28,33]. Findings in the histological analysis of our case was consistent with the above mentioned characteristics, therefore a definitive diagnosis of odontogenic myxoma was obtained.
Treatment approaches for odontogenic myxoma remain surgical. However, it can vary from more conservative approaches like enucleation and curettage, to radical resection with wide margins of 1.0-1.5 cm. Although medical management of odontogenic myxoma including chemotherapy has been utilized in few recurrence cases, its use is not advocated [5,34]. Furthermore, due to the radio-resistant trait of odontogenic myxoma, radiotherapy also has no role in management of this lesion [1,21,26]. Boffano et al. [35] have advocated resection of myxomas larger than 3 centimeters, and enucleation and curettage of lesions smaller than that. The idea behind utilization of these rather contrasting approaches originates from the growth and permeation characteristics of odontogenic myxoma, depriving this lesion from a well-defined border. Furthermore, radical resection not only leaves the patient with significant cosmetic and functional defects, but also it is not always successful in preventing recurrence of the lesion [5,36]. Current literature suggests that aggressive management of this lesion may not be necessary, especially as first-line approach [5]. Allphin et al. [37] suggested a more conservative approach as the first-line treatment of odontogenic myxoma, followed by respective surgery if deemed necessary. However, when radical surgery is performed, delayed reconstruction must be considered due to odontogenic myxoma’s high tendency to recur [6]. Utilization of liquid nitrogen cryotherapy has also been recently reported in adjunct to surgical modalities [20]. In our case, enucleation and curettage accompanied with peripheral ostectomy and concomitant burnishing of teeth roots was utilized.
Odontogenic myxomas are notorious for their very high recurrence rate, consisting up to 25% following enucleation and curettage alone [38,39]. Therefore, follow-up is recommended throughout the patient’s life [5,40]. However, at minimum a follow-up period of 5 years is highly recommended, since this the time period where majority of recurrences occur [6]. Our patient was recalled to the clinic for the first and second year follow-ups, both of which revealed no signs of recurrence.