Surface Aneurysmal Bone Cyst: Clinical and Imaging Features in 10 New Cases

Abstract

Aneurysmal bone cyst originating from the surface of the bone, either within the cortex or subperiosteally, is an uncommon anatomic subtype. This article reports the clinical and radiologic evaluations and treatment outcomes of 10 patients with surface aneurysmal bone cysts that were surgically treated between 1982 and 2014. Mean age at the time of surgery was 22.4 years (range, 11-44 years). According to Capanna's radiographic evaluation criteria, 6 of the lesions were classified as type V and 4 were classified as type IV. Radiographically, periosteal shell formation was observed to be complete in 4 patients, partial in 3, and absent in 3, and 6 patients had Codman's angle or buttress formation. In 1 patient, computed tomography scan showed birdcage-like ossification attached to the surface of bone. Magnetic resonance imaging showed fluid-fluid levels in 5 patients. All of the patients had standard curettage and high-speed burr application as an adjuvant. No patient had local recurrence at the end of the follow-up period of 98.4 months (range, 13-288 months). These findings show the importance of careful radiologic evaluation and biopsy to better plan a treatment strategy when surface aneurysmal bone cyst is included in the differential diagnosis. The finding of fluid-fluid levels on magnetic resonance imaging or computed tomography is not pathognomonic for primary aneurysmal bone cyst; however, the absence of this finding does not rule out the diagnosis. The rate of local recurrence after curettage plus high-speed burr is reasonably low, and other adjuvant procedures should be used whenever needed. [Orthopedics. 2016; 39(5):e897-e903.].

Rare aneurysmal bone cysts: multifocal, extraosseous, and surface variants

“…Surface ABCs extend beyond the confines of the outline of the bone and arise within the cortex of the bone or beneath the periosteum, limited by periosteum externally and endosteum internally [64][65][66]. They were initially referred to as parosteal type in the radiographic classification of ABCs [67] and were named subperiosteal giant cell tumor [31] or subperiosteal osteoclasia [32].…”

“…In the radiographic classification developed by Capanna et al [1,30], surface ABCs were described as types IV and V. According to this classification, type IV lesions include subperiosteal forms that develop away from the bone so that the cortex is either intact or superficially eroded. Type V lesions develop both peripherally toward the periosteum and centrally toward the medulla so that the cortex is penetrated [30,[64][65][66]. Maiya et al [64] described a cortical metaphyseal ABC that showed similar degrees of intraosseous and extraosseous extension and tended to be more aggressive than subperiosteal ABCs.…”

“…They also described a mixed pattern ABC that was not possible to distinguish their precise origin in that they either presented with features suggestive of one pattern and then developed features of the other. Fifty cases of surface ABCs have been reported in the related literature (Table 3) [34,39,42,52,[64][65][66]. In our practice, we have treated seven patients with surface ABCs; six patients had periosteal ABCs (Figs.…”

“…CT scan showed an abnormality of the soft tissue protruding from the bone cortex with a thin rim and a density, suggesting the presence of a calcified mass and slightly irregular wall. The erosion of the cortex did not extend to involve the medulla [31,34,39,52,[64][65][66]. MR imaging showed a well-defined circumscribed lesion sometimes scalloping the outer cortex without breaching it.…”

“…The peri-tumoral soft tissue showed significant swelling and enhancement along the periosteum with blood-filled spaces of varying sizes with numerous fluid-fluid levels, T1/T2 hypointense septa, and T1/T2 hypointense calcified rim with some septal enhancement. In contrast, the lesions showed a predominantly high signal intensity with well-defined margins on T2-weighted images; the signal intensity of the intralesional septa was low to intermediate, while the signal intensity of the separated areas was high [31,34,39,52,[64][65][66].…”