This article reports the case of a large aneurysmal bone cyst (ABC) in a 12‐year‐old girl, who came to the Ophir Loyola Hospital (Belém, Pará, Brazil) complaining of pain and debilitated because of a secondary infection. Radiographic and tomographic findings presented an expansion/destruction pattern, including a slight narrowing of the oropharynx and destruction of the right mandibular condyle and coronoid process, which according to the literature are rarely affected by this type of cyst. Because of the size and progression of the cyst, the treatment included block resection with a costochondral rib graft. The clinical and radiographic aspects of expansion with destruction, associated with trans‐surgical moderate bleeding and the histopathological findings (dense connective tissue and numerous blood spaces) led to a final diagnosis of a mixed type ABC.

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