Aneurysmal cyst of bone, a complex histopathological lesion – case presentation, differential diagnosis and correlation of imaging data.

Aneurysmal bone cyst (ABC) is a benign osteolytic, expansile, sometimes destructive but self-limited bone lesion, composed of blood-filled channels and cystic spaces that are separated by stromal fibrous septae. We present the case of a 29-yearold female patient who discovered a deformity of the left forearm after trauma. The imaging data (simple radiography and whole-body scintigraphy) suggested the following diagnosis: low-grade central osteosarcoma, eosinophilic granuloma, Ewing sarcoma or osteoblastoma. The histologic examination of the bone biopsy showed a benign vascular lesion with overlapping features of ABC and osteoblastoma with ABC-like changes. The immunohistochemical tests (CD31, CD56, SATB2, MDM2, CD45 and Ki-67) were in favor of aneurysmal bone cyst, but they could not definitively exclude an osteoblastoma with ABC-like changes. We discuss each of the aforementioned differential diagnoses from the histopathological point of view, and we found arguments favoring both ABC and osteoblastoma with ABC-like changes. We conclude on the importance of correlations between the imaging data and the histopathological diagnostic. [ABSTRACT FROM AUTHOR]