Use of magnetic resonance imaging and histopathologic findings for diagnosis of an aneurysmal bone cyst in the scapula of a cat.

CASE DESCRIPTION: An 18-month-old spayed female domestic shorthair cat was evaluated because of left thoracic limb lameness.

CLINICAL FINDINGS: A firm mass was palpable in the left scapular region. On the basis of clinical signs; results of radiographic, ultrasonographic, and cytologic evaluations; and findings on magnetic resonance imaging, an aneurysmal bone cyst (ABC) of the scapula was strongly suspected.

TREATMENT AND OUTCOME: Considering the large size of the mass and the poor prognosis for return to function of the left thoracic limb, amputation was elected. Histologic evaluation ruled out a malignant process and was diagnostic for ABC originating from the left scapula. The patient recovered well and was ambulatory the day after surgery. Three years after surgery, the cat was healthy.

CLINICAL RELEVANCE: The combination of radiography, regional ultrasonography, and magnetic resonance imaging enabled lesion structure and cavity content evaluation. However, final diagnosis was confirmed by histologic evaluation. To our knowledge, this is the first veterinary report of the use of magnetic resonance imaging in the characterization and diagnosis of an ABC.