COM April 2006 Diagnosis

Expansile and Radiolucent Lesion in the Left Anterior Maxilla

Can you make the correct diagnosis?

This is a 28-year-old white male who presented with a bony bump above teeth #s 10 and 11. This lesion was first noticed by his general dentist in September 2004 and later by the oral surgeon on 10/30/2005. It was expansile, especially labially. The bone supporting the two teeth was compromised, but the teeth were not mobile. The area was biopsied on 11/02/2005. The area was described as a solid mass with a gelatinous consistency. It was 2 x 1.5 cm in size. The lesion did not perforate into the maxillary sinus or the nasal cavity. The roots of teeth #s 10 and 11 were devoid of bone on the interproximal surfaces and a significant amount of the labial cortex was missing. The patient is on follow-up in 3-month intervals.

1. Globulomaxillary Cyst

Sorry, this is not the correct diagnosis.

Globulomaxillary cyst was described by Thoma as a developmental (fissural) cyst. The fissural original has been disputed (1, 2). Today, the literature almost uniformly agrees that the entity of globulomaxillary cyst should only be used as a clinical descriptive name. According to Wysocki, the majority of the lesions (over 80%) presenting with the radiographic features of a globulomaxillary cyst are of periapical origin. Histologically, it can be a variety of odontogenic lesions predominantly of periapical origin, i.e. periapical cyst and granuloma, odontogenic keratocyst, or more rarely odontogenic myxoma, squamous odontogenic tumor, adenomatoid odontogenic tumor or central giant cell granuloma (the latter is not of tooth origin) (1, 3). The evidence in the literature is in favor of this lesion being predominantly of tooth origin (1-3). Anatomically, this lesion specifically occurs at the junction of the globular portion of the medial nasal process and the maxillary process, the globulomaxillary process area, between the maxillary lateral and canine teeth (1-3). The lesion is usually discovered during routine dental examination. It is asymptomatic, but becomes slightly tender if infected. Radiographically, this lesion has a distinct appearance which is an oval, round, or inverted pear-shaped radiolucency between the roots of the lateral incisor and cuspid teeth, causing divergence (1-3). Bilateral lesions are reported, but rarely (1, 3). The definitive diagnosis is based on the histology which in turn varies depending on the specific entity. It is usually an entity of tooth origin as described above. However, it can be of bone and non-tooth origin, as in the case of central giant cell granuloma. Treatment and prognosis is based on the specific entity. The histology in this case is not supportive of a periapical lesion.

2. Squamous Odontogenic Tumor

Sorry, this is not the correct diagnosis.

Squamous odontogenic cyst was first diagnosed by Pullon and Shafer in 1975. It is important to note that SOT can be misdiagnosed as acanthomatous ameloblastoma or intrabony squamous cell carcinoma. Therefore, it is particularly important to differentiate between the clinical and radiographic findings of an ameloblastoma and intrabony squamous cell carcinoma in comparison with that of SOT (4-6). The latter is a non-aggressive benign neoplasm that can occur at any age (with a range of 11-67) with equal gender distribution (4). Both jaws are affected equally and it is usually associated with mild pain and tenderness (4-5). About 25% of cases are asymptomatic (4-6). Tooth mobility and multiple lesions have been described (4, 6). Radiographically, it usually presents as a relatively demarcated radiolucency, sometimes semicircular or triangular in shape (4). It is usually not corticated. These features are readily distinguishable, both clinically and radiographically, from a solid ameloblastoma as well as a malignant intrabony epithelial neoplasm. It is histologically made up of epithelial islands of variable shapes and sizes. The cells comprising these islands are well differentiated and squamous in type. The periphery of these islands is flat (4-6). Simple curettage is adequate treatment for this lesion and has a good prognosis. The histology in this case is not supportive of SOT

3. Odontogenic Keratocyst

Sorry. You are Incorrect!

Odontogenic keratocyst (OKC) is an aggressive odontogenic cyst and is known for its rapid growth and its tendency to invade the adjacent tissues, including bone. It has a high recurrence rate and is associated with basal cell nevus syndrome (7, 8). OKCs typically occur in the age ranges of 20-29 and 40-59, but cases in patients ranging in age from 5 to 80 years have been reported. The distribution between sexes varies from equal distribution to a male-to-female ratio of 1.6:1, except in children (7,8). OKC predominantly affects Caucasian populations. OKC may occur in any part of the upper and lower jaw, with the majority of cases (almost 70%) occurring in the mandible. They occur most commonly in the angle of the mandible and ramus (7). Radiographically, OKCs present predominantly as unilocular radiolucencies with well defined or sclerotic borders. OKCs of the maxilla are smaller in size when compared to those occurring in the mandible; larger OKCs tend to expand bone, but mildly—obvious clinical expansion should be viewed with suspicion for a neoplasm. Odontogenic keratocysts are significant clinical entities due to their tendency for recurrence and destructive behavior. They are known to have a high recurrence rate, ranging from 13% to 60% (7, 8). Complete surgical removal is the treatment of choice. Surgery combined with Carnoy’s solution or liquid nitrogen cauterization has been effective in reducing the recurrence rate (8, 9). Resection is a rare modality of treatment. Most cysts recur within the first three years while others may recur as late as after 16 years (7-9). Conservative surgical removal and long-term follow-up is the treatment of choice by most clinicians. The histology in this case is not supportive of OKC.

4. Odontogenic Myxoma

Congratulations, you are correct!

Odontogenic myxoma should not be mistaken for soft tissue myxoma, which is a relatively common lesion of the soft tissue but is rare in the mouth; it occurs more commonly in areas such as the heart. When it does occur in the mouth, odontogenic myxoma occurs in the jaw bones, usually in the tooth-bearing areas of the jaw (10-12). It is an uncommon, benign, but locally aggressive neoplasm. Nearly all cases so far have been described in the jaw bones. Therefore, it is of tooth origin, and is believed to be from the mesenchymal portion of a tooth germ, most likely of the dental papilla. It has the potential for extensive bony destruction and extension into the surrounding structures (10-12). It is less common than odontomas and ameloblastomas, constituting around 17% of all odontogenic tumors. For that reason, a pathologist who is not familiar with the histology of a tooth germ can mistake a myxoid dental follicle for an odontogenic myxoma. Almost 75% of odontogenic myxomas occur in patients around 23-30 years of age with a slight female predilection (1:1.5 male-to-female ratio) (10-12). It rarely occurs in patients over 50 or under 10 years of age. It occurs almost equally in the maxilla and mandible with a slight predilection for the posterior mandible. A few cases are described in the ramus and condyle, which are non-tooth bearing areas.

Odontogenic myxoma is slow-growing, persistent and destructive. Most cases are expansile and can displace and resorb teeth. In the maxilla, they usually invade the maxillary sinuses and at times (though rarely) cross the midline to the opposing sinus. Radiographically, the majority present as expansile and multilocular, though some are unilocular with or without scalloped borders, and rare cases present with a diffuse and mottled appearance which can be mistaken for a malignant neoplasm. Grossly, this lesion is gelatinous in nature, making curettage alone difficult; the more fibrotic odontogenic myxomas (also known as odontogenic myxofibroma or fibromyxoma) have more body and are easier to curette. Histologically, it is made up of loose and delicate fibrous connective tissue. The fibroblasts are stellate and are suspended on a delicate network of collagen fibrils. Immunohistochemistry studies suggest that the spindle-shaped cells constituting this neoplasm have a combined fibroblastic and smooth muscle typing, suggesting that it is of myofibroblastic origin (12). Small blood vessels are present, as are small odontogenic epithelial islands on occasion. Sometimes, this lesion is fibrotic, making it easier to curette.

The treatment of choice is surgical excision ranging from segmental resection with clear bony margins of up to 1.5cm to prevent recurrence of the neoplasm. Curettage with and without cauterization is used for treatment, but is associated with a higher recurrence rate compared to the resected lesions. Reconstruction can be immediate or delayed, and can include an autologous bone graft from the anterior or posterior iliac crest. Fibula-free vascular osteocutaneous bone graft is another reconstructive modality, as is distraction osteogenesis. Immediate postoperative follow-up is weekly for approximately one month, then monthly for the next five months and twice a year for the next five years.


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