What Are the Myxofibromas of the Jaws?
Myxofibromas (MFs) of the jaws are benign odontogenic (dental origin) tumors with mesenchymal (connective tissue cells) origin. They were first described by Virchow in 1863. MFs are considered variants of odontogenic myxoma (another rare jaw tumor). These tumors comprise a considerable amount of collagen fibers dispersed within a myxoid tissue (fatty tissue) stroma. MFs are accountable for around 2.3 to 17.7 percent of all odontogenic jaw tumors.
What Are the Clinical Features of Myxofibromas of the Jaws?
MFs are slow-growing, benign (non-cancerous), and expansile lesions occurring in the mandible (lower jaw) or the maxilla (upper jaw). These may present with tooth displacement or root resorption. MFs are found within the intraoral (inside the oral cavity) regions, mainly the posterior (back) mandible (lower jaw bone). These tumors rarely have extraoral involvement or margins. The maxilla (the upper jaw) and the anterior (front) mandible are rarely affected. MFs can be diffuse or well-defined. These are characterized by gelatinous grayish-white tissue inside the tumor. The content of the tumor replaces the spongy bone and can also displace the cortical plates (bony plates) of the jaws. When this tumor involves the adjacent teeth, tooth root displacement and resorption may be present. MFs represent only a fraction of entire myxomas. However, they are the most frequent in the myxoma tumors category. Also, MFs have a recurrence rate between 25 and 43 percent. Although the mandible and maxilla are the two most common sites of involvement, they can also occur in the parotid glands (a type of salivary gland), nasal cavity, paranasal sinuses, and pharynx.
What Is the Etiology of Myxofibromas of the Jaws?
Most research states that the lesion is primarily derived from the neural sheath (a layer of myelin and connective tissue). As a result of degeneration of fibromas, lipomas, chronic irritation, or tissue death in the jaw bone, these tumors are formed. Recent studies implicate that MFs arise from the mesenchymal tissue of the dental follicle. Hence, they are described as having an odontogenic origin, with fibroblasts (the most common connective tissue cells) playing a crucial role in tumor cell circulation.
What Are the Investigations for the Myxofibromas of the Jaws?
MFs can be diagnosed through different methods: radiological, histological, or immunohistochemical.
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Radiological: The radiological investigation of these tumors reveals the lesions to have a homogenous (uniform) radiolucency (black area within the bone). One may find a ‘honeycomb,’ ‘soap bubble,’ and ‘tennis racket’ appearance on a radiograph (X-ray). Radiological examination plays a crucial role in the differential diagnosis (the process of differentiating similar conditions) of MFs from other benign myxomas and neoplasms (cancers) associated with myxomatous tissues of the jaw.
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Histological: Myxofibroma comprises widely spaced star-shaped, triangular, or tapering cells with long branching processes and abundant mucin (a protein). The tumors also contain round and evenly spaced embryonic cells.
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Immunohistochemistry: In immunohistochemistry (IHC), antibodies are determined against specific biological tissues (neural, muscular, epithelial, or mesenchymal). As most of the tumors have a mesenchymal origin, the evaluation is done by the presence of vimentin (a protein expressed in mesenchymal tissue).
What Is the Differential Diagnosis of Myxofibromas of the Jaws?
The differential diagnosis for odontogenic jaw tumors is quite challenging. Hence, the pathological conditions included for a differential diagnosis are:
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Metastatic (malignant) jaw neoplasms.
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Ameloblastoma (a rare benign jaw tumor).
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Central hemangioma of the jaw (a rare benign blood vessel tumor).
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Odontogenic cysts (a cyst is a pathological cavity containing fluid, gas, or solid material).
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Fibrous dysplasia (a bone condition in which abnormal fibrous tissue replaces normal bone).
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Aneurysmal bone cyst (ABC, blood-filled bony lesion).
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Central giant cell granuloma (CGCG, a localized bony jaw lesion).
A confirmative diagnosis is crucial in the identification and correct treatment of MFs. However, through MRI, computed tomography (CT), or cone beam computed tomography (CBCT), the radiographic diagnosis can lead to the final diagnosis.
What Is the Management of Myxofibromas of the Jaws?
Treatment options include conservative approaches to maximal jaw structure preservation or surgical removal. The surgical removal of the jaw lesion and curettage (scraping the inner lining) of the cavity is done to eliminate the extensive tumors. Tumor excision involves the extraction of the involved teeth around the portion of the affected jaw. It must be noted that the conservative approach is associated with a higher recurrence rate of (up to 25 percent). Further, recurrence of these tumors occurs mostly during the first two years after the treatment. The following points are pertinent.
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The treatment is mainly surgical and involves both enucleation (surgical removal) and curettage of the lesion to avoid recurrence. Therefore, many oral surgeons recommend that the myxoma lesion must be completely resected.
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Complete resection depends on the size and behavior of the tumor. Usually, the oral surgeon leaves a margin of about 1.5 to 2 centimeters (cm) of healthy bone during resection for proper healing. Also, the patient should be monitored after complete resection for at least two years (because of the highest recurrence rate during this period).
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If any defects of the maxilla are present under 5 cm, these defects need to be reconstructed by a buccal fat pad flap (an area from the cheek for the reconstruction of maxillary defects due to a tumor).
Conclusion:
Myxofibromas are uncommon lesions and present interesting diagnostic problems for the clinician and pathologist. These slow-growing tumors consist of a mucoid ground substance with some collagen, the amount of which depicts the reason they are called myxofibromas. However, the exact origin of these benign tumors is unclear. A majority of MFs occur without symptoms. Still, a few patients have increasing pain secondary to the invasion of surrounding structures. Hence, timely detection and proper management can prevent the associated morbidity and high recurrence.
