Review Question - QID 210211

This patient's imaging and histology is consistent with an aneurysmal bone cyst (ABC). The patient should undergo extensive curettage, use of a high-speed burr to destroy the cyst lining, and placement of allograft bone.

The treatment of ABC is typically aggressive curettage, adjuvant treatment, and placement of allograft bone. Adjuvant treatment with phenol, liquid nitrogen, argon beam, or high-speed burr is suggested to help kill/remove microscopic residual tumor cells and lower the risk of recurrence. Arterial embolization prior to resection of large lesions has shown some benefit to decrease bleeding at the time of surgery. Arterial embolization alone has also been demonstrated to lead to lesion resolution in some cases. Alternative treatment modalities include en-bloc resection, sclerotherapy, and radionuclide therapy in certain situations.

Rapp et al. review the diagnosis and management of ABCs. ABCs most frequently occur in adolescent patients and present as a painful, expansile, and palpable mass. They report that even after extensive treatment, there is a 20-30% rate of recurrence. Risk factors for recurrence include less aggressive curettage (due to proximity to physis/articular surface), increased cellularity (in giant cells and stromal cells), and increased mitotic figures.

Erol et al. report on the outcomes of 64 children with aggressive ABCs that underwent surgery. 92% underwent extended intralesional curettage and grafting. The authors found a recurrence rate of 7% and functional outcome scores of 95/100. Proximity to the growth plate was the only factor predictive of recurrence. This study demonstrates that aggressive curettage and bone grafting leads to excellent outcomes with low rates of recurrence and complications.

Figure A is an x-ray of the pelvis demonstrating a multiloculated radiolucent lesion in the left iliac wing. Figures B-D are axial, coronal, and sagittal MRI cuts demonstrating fluid-fluid levels in the left iliac wing, classic for ABC. Figure E is a histology slide demonstrating lakes of red blood cells separated by fibrous septa with benign-appearing spindle cells and occasional giant cells, consistent with aneurysmal bone cyst.

Incorrect Answers:
Answer 1: Chemotherapy is not indicated for ABCs.
Answer 2: Wide resection and reconstruction can be considered for patients with ABCs (this would nearly eliminate the risk of recurrence). Despite the proximity to the acetabulum, this adolescent patient should be given a chance at a more limited procedure that would better preserve function and have a lower infection risk.
Answers 3: Due to the benign nature of this tumor, external beam radiation is not typically used. Radiation therapy is known to increase the risk of malignant transformation. There is evidence supporting the use of radionuclide ablation of axial ABCs.
Answer 4: The biopsy is not consistent with infection, therefore, antibiotics are not appropriate.