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.