Aneurysmal Bone Cyst (ABC), A Rare Diagnosis in Oral Pathology Based on Our 15-Year Institutional Experience

Abstract

Abstract Introduction/Objective Aneurysmal bone cyst (ABC) is a rare, benign bone lesion that was first described by Jaffe and Lichtenstein in 1942. Primary ABC usually affects vertebrae and metaphyseal regions of long bones, particularly femur and tibia. Only 2-3% of ABCs occur in the head and neck region, with the mandible and maxilla being the most common. It arises mostly in children and young adults, mean age 20 yo, with no gender predilection. ABC can manifest with pain, swelling, and pathological fractures. Radiographically, it appears as a metaphyseal expansile lesion that thins the cortex and has a sclerotic rim. Lesions containing “fluid-fluid” levels are best appreciated on MRI. Approximately 70% of primary ABCs have rearrangements of the USP6 gene. The most common translocation seen in primary ABCs is t(16;17) (q22;p13) leading to the fusion of the cadherin 11 gene with USP6 gene. The USP6 gene product inhibits the differentiation of osteoblasts and dysregulates bone morphogenetic protein signaling pathway. Methods/Case Report A retrospective chart review of all oral pathology cases referred to our institution between 1996 and 2022 was performed; three patients diagnosed with primary ABC were identified. Patient demographic data, clinical presentation, treatment, slides, and pathologic features were reviewed. Results (if a Case Study Enter NA) We report of three primary ABCs of the mandible and maxilla. The mean age was 39 yo (range, 26-59 years). The mandible was affected in two cases, and the maxilla involved in one. Female: Male ratio was 2:1. All lesions were primary ABC, with no other associated lesion - they showed pseudocystic structures with fibrous stroma and a variable numbers of multinucleated giant cells in relation to sinusoidal blood spaces, as well as irregular trabeculae of osteoid and reactive woven bone. Conclusion Primary ABC is a rare tumor in oral pathology. The importance of this study is to increase awareness of this neoplasm in the head and neck region, as well as delineate features that help differentiate ABCs from other fibro- osseous lesions of the mandible and maxilla.