A 22-year-old female patient presented with a selling on the right side of the chin which is gradually increasing in size. She did not have any previous history of trauma. On examination, facial asymmetry was present with a firm, non-tender swelling involving the right side of the lower jaw. On aspiration, blood-tinged fluid was obtained.
CT was done which showed a well-defined, oval, expansile lytic lesion involving the left angle of mandible on the bone window. The cortex was thinned out with multifocal discontinuity and internal septations. The lesion showed narrow zone of transition without any periosteal reaction (Figure1). On soft tissue window, the lesion showed multiple internal septations and blood-fluid levels (Figure 2).
Background
An aneurysmal bone cyst is characterized by blood-filled, non-endothelial spaces that may contain osteoid tissue and osteoclast-like giant cells [1]. ABCs in the craniofacial skeleton are uncommon unlike the long bones and spine. Mandible is involved in only 2% of the cases, body (90%) and mandibular ramus(10%) being the main locations [2]. ABC can be primary or secondary. All the cases of primary ABC exhibit a thinning of the cortex and an expansion of the lesion. Secondary ABCs can be morphologic mimics of a primary ABC and arise secondary to a pre-existing bone lesion, which can be of malignant nature.
Clinical Perspective
Clinical presentation of the ABC varies from a small, indolent, asymptomatic lesion to rapidly growing, expansile, a destructive lesion causing pain, swelling, deformity, neurologic symptoms, pathologic fracture [3].
Imaging Perspective
Radiographs demonstrate sharply defined, expansile osteolytic lesions, with or without thin sclerotic margins which is known as the soap-bubble appearance. CT helps in assessing cortical breach, matrix calcification. Internal content, septations and fluid-fluid level can also be seen within the lesion. The primary variant shows imaging features same as the previously mentioned features of ABC while the secondary variant may show features of the accompanying lesion. T2-weighted MR images show multiple cystic lesions that are divided by a thin septum, and fluid-filled cysts that indicated collection of blood. Malignant transformation of ABC is rare, but can raise a discussion about a missed primary lesion with secondary ABC. The red flags for secondary ABCs include presence of numerous blood-filled cavities divided by septa, cortical destruction and the presence of a soft tissue mass and thick septal enhancement, as observed using MRI. Thus, contrast-enhanced MRI is important in differentiating primary and secondary ABC.
Outcome
Primary ABC shows an overall cure rate of 90%-95% [4]. Complete excision of lesion is the main aim of treatment. The treatment modalities are percutaneous sclerotherapy, diagnostic and therapeutic embolization, curettage, block resection & reconstruction, radiotherapy and systemic calcitonin therapy. The recurrence rate of aneurysmal bone cysts is up to 20% [5]. In our case curettage of the lesion was done and on histopatholgical examination, endothelium-lined vascular spaces with abundant pools of RBC were seen. Giant cells with hemosiderin pigments was also seen which is characteristic of ABC.
Take Home Message / Teaching Points
ABC is a rare entity among the lesions involving the mandible and because of its characteristic appearance can be diagnosed promptly on imaging. Presence of extra-lesional soft tissue component, presence of osteoid/chondroid matrix, enhancing solid components among fluid-fluid levels raise the suspicion of secondary ABC rather than the primary ABC.
Aneurysmal bone cyst of mandible
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Based on the provided axial CT images, a lesion with relatively clear boundaries and expansive bone destruction is observed in the right mandible. The interior of the lesion shows uneven density, with some separations (valve-like or “bubbly” structures). Localized cortical bone thinning and bulging are noted, but no clear evidence of widespread soft tissue invasion is identified. Certain slices reveal hemorrhagic or fluid layering, suggesting components related to blood or fluid.
Considering the patient’s clinical presentation (a young female under 25, gradual painless swelling in the right mandible, and bloody aspirated fluid), the combination of radiological and clinical features strongly suggests the characteristic expansive, cyst-like appearance commonly seen in an Aneurysmal Bone Cyst (ABC).
Typically occurring in young individuals, it often appears as an expansive bone lesion with blood-filled cystic spaces. Radiologically, cortical thinning and outward expansion can be seen, and the lesion often demonstrates multiple septations or fluid-fluid levels. In this case, the aspirated bloody fluid further supports this diagnosis.
Giant cell tumors commonly occur in young adults and often involve the epiphyseal region of long bones, but can also appear in the mandible. Although they can show expansive changes and osseous destruction, they typically lack significant fluid-fluid levels, and aspiration usually yields solid or non-bloody material.
Such lesions in the mandible can also present with low-density changes or altered bone structure, but they often display a “ground-glass” appearance and do not typically yield bloody fluid upon aspiration. They are less characteristic than an ABC in this scenario.
Based on the patient’s age (young female), progressive painless mandibular swelling, bloody aspirate, and radiological features—supported by pathology—this lesion can be confirmed as an Aneurysmal Bone Cyst (ABC). If pathology indicates no malignancy or other primary lesion, it can be considered a primary ABC.
The treatment goal is to remove or reduce the lesion, stabilize the bone structure, and minimize recurrence. Main treatment approaches include:
Rehabilitation/Exercise Prescription Recommendations (Based on FITT-VP Principle):
Throughout the rehabilitation period, be alert for sudden worsening pain, significant swelling, or unusual bleeding. If any such symptoms occur, seek immediate medical attention to rule out recurrence or other complications.
This report serves only as a reference based on the currently provided imaging and clinical information. It cannot replace an in-person consultation or professional medical advice. Any treatment or medication must be administered under the guidance of a qualified physician.
Aneurysmal bone cyst of mandible
