A rare presentation of a simple bone cyst.

Simple bone cyst is an oft-described entity, which goes by many sobriquets and has been presented in the literature as early as 1926. It is a lesion of unclear etiology with many proposed hypothesis for its pathogenesis and nonspecific histopathological presentation. We present a case of a solitary bone cyst, which clinically presented as a solitary lesion, but radiological examination revealed multiple lesions peppering the maxilla and the mandible, thereby highlighting the importance of atypical presentation and "surprise" lesions that may show up on radiological examination.

Simple bone cysts (SBCs) of the jaw were initially described as an entity in 1926 by Lucas and Blum and later qualified in 1946 by Rushton as a single cyst that has no epithelial lining, has an intact bony wall, is fluid filled and has no evidence of acute or chronic inflammation.[12] Various synonyms of SBCs are traumatic bone cysts, hemorrhagic bone cysts, solitary bone cysts, progressive bone cysts, extravasation cysts, unicameral bone cysts, and SBCs.[234]

As implied by the name, there is no clear etiology for these lesions. Specifically, trauma has been ruled out as a cause of idiopathic bone cavities (IBCs) because the incidence of these lesions in patients with prior trauma is the same as that in the general population.[2] Other hypotheses include a blockage of lymphatic drainage from venous sinusoids leading to resorption of bony trabeculae, developmental anomalies resulting in synovial fluid being incorporated intraosseously, and osteolysis secondary to altered bone metabolism.[56] These lesions are usually an incidental finding discovered during routine radiographic examination, most commonly in a patient's second and third decade of life. There is no gender predilection.

Radiographically, these lesions present as well demarcated, unilocular radiolucencies that frequently scallop adjacent teeth roots, which are vital without evidence of resorption or displacement. This finding distinguishes IBCs from more worrisome odontogenic lesions.

Histologically, no signs of the epithelium will be found, although fibrous tissue lining may be observed. Sometimes myxomatous changes and fragments of vital bone are observed.[4]

Treatment involves surgical exploration that typically reveals an empty cavity with smooth walls. A thin fibrous lining or the mandibular neurovascular bundle may be observed. Serosanguineous fluid may be aspirated as well. Often the final diagnosis and treatment are completed in the same surgical procedure.[4]

Case Report

A 50-year-old female patient was referred to our Department of Oral Medicine and Radiodiagnosis with a complaint of a painless swelling over the right mandibular region since 3 months. Her past dental history revealed extraction 5 years ago. Medical history was not contributory. Intraoral examination revealed a swelling in relation to the right mandibular posterior region extending from the region of 45 to 48 posteriorly and left mandibular posterior region extending from 35 to 38 [Figures 1 and 2]. On palpation, expansion of buccal and lingual cortical plates was observed. Vitality tests for the associated teeth proved to be positive. A Panoramic radiograph was taken to view the apparently isolated lesion on the mandibular right posterior region. The radiolucency observed in the region of right mandibular posteriors was multilocular with sclerotic borders extending posteriorly up to the anterior border of the ramus with the superior wall scalloping between the roots of 44 and 47 region. In addition to the suspected multilocular radiolucency, orthopantomographs revealed bountiful lesions; multiple radiolucencies were noted in the anterior maxilla and lower left body of the mandible [Figure 3]. Computed tomography (CT) scan revealed the bilateral involvement of the posterior aspect of mandible [Figure 4] and anterior aspect of maxilla [Figure 5] showing bicortical expansion in relation to right and left posterior mandible. A clinical diagnosis of the traumatic bone cyst with differential diagnosis of central giant cell granuloma and odontogenic keratocyst was rendered.

Figure 1

Intraoral examination revealing swelling in the right mandibular posterior region

Figure 2

Intraoral examination revealing swelling in the left mandibular posterior region

Figure 3

Orthopantomographs showing multiple radiolucencies

Figure 4

Computed tomography image showing mandibular lesion

Figure 5

Computed tomography image showing maxillary lesion

Patient was offered a choice of surgical exploration and biopsy. Surgery revealed empty cavities [Figures 6–8]. Curettage of the cavities was done, and the obtained connective tissue material was sent for histopathological examination, which revealed densely inflamed connective tissue stroma with extravasated red blood cells, necrotic changes, and chronic inflammatory cells. However, there was no evidence of any cystic epithelium.

Figure 6

Surgical exploration of the lesion in right mandible

Figure 8

Surgical exploration of the lesion in maxilla

Surgical exploration of the lesion in left mandible

Patient made an unremarkable recovery after surgery. Follow-up radiographs after a period of 6 months showed 90% of bone regeneration [Figure 9].

Figure 9

Orthopantomographs showing bone regeneration at the surgical site after 6 months

Discussion

Comparing our data with the literature review, an interesting finding of SBCs in an older age group that were not associated with cement-osseous dysplasia is rare, such variation in the clinical presentation of SBCs may be relevant to the better understanding of this underexplored lesion.[7]

These lesions showed radiographic characteristics that suggested differential diagnoses of ameloblastoma, odontogenic keratocyst tumor or a central giant cell lesion in view of their location. Due to these radiographic characteristics, CT imaging is important for an accurate diagnosis, as this may avoid unnecessarily aggressive surgical approaches, like en bloc resections of the mandible.[8]

Suei et al. found that most recurrences were seen within 5 months of the surgical treatment, and this group recommended that follow-up should be continued until healing was confirmed radiographically within 3 years.[9] In our sample, evidence of new bone formation after surgery was noticed within 3 months of the surgery and complete healing was noticed radiographically.

The most common radiographic finding in multifocal SBCs was scalloping, consistent with what is traditionally described in single lesions.[10] Bony expansion and multilocular radiolucent patterns were observed.[11] In general, SBCs have a tendency to grow along the long axis of the bone, causing minimal expansion; however, expansion of the involved bone can occur and is more common with larger lesions.[10]

In general, the mandibular body is by far the most common location for SBCs, with the maxilla representing an uncommon site.[512] One explanation for this lower prevalence in the maxilla could be related to the possibility that maxillary lesions are obscured by the overall radiolucent appearance imparted by the maxillary sinus.[121314] Another possible explanation could be due to differences in the quality and amount of bone marrow and vascularity in the maxilla compared to the mandible.[15] In this case, we noted that multiple SBCs in the mandibular body, as well as maxilla.

Curettage of the bone walls is the most widely accepted approach to the management of SBCs of the jaws, the goal being to promote the formation of a blood clot and subsequent bone repair.[1116] In addition, application of Gelfoam, grafting of allogenic bone with platelet-rich plasma and intralesional injections of a mixture of blood, porous hydroxyapatite, and bone fragments have been reported to produce good results.[171819]

Conclusion

In general, all maxillofacial lesions present with a standard set pattern of clinical or radiographic presentations. However, this case defies the “regular standards” set for a traumatic bone cyst. Proper recording of case history, knowledge of symptomatology, and correct radiographic interpretation will be helpful for proper diagnosis and management. Being open to all probabilities and possibilities would be an added advantage.