Fibromyxoid areas and immature osteoid are associated with recurrence of primary aneurysmal bone cysts.

Aims: Primary aneurysmal bone cysts have a high recurrence rate following curettage. The aim of this study was to determine clinicopathological features associated with recurrence of aneurysmal bone cysts.

Methods And Results: The clinicopathological features of 86 patients (37 males, 49 females, age range 5-62 years) with aneurysmal bone cysts were reviewed. Recurrence rates following curettage and excision were 32.7% and 5.6%, respectively (P = 0.028). The association of clinicopathological features with recurrence was studied in a subset of 45 patients treated by curettage. The presence of nodular fasciitis-like fibromyxoid areas [P = 0.033, odds ratio (OR) = 9.17, 95% confidence interval (CI) 1.06, 79.39] and immature osteoid with active osteoblasts (P = 0.041, OR = 3.7, 95% CI 1.03, 13.35) was significantly associated with an increased risk of recurrence. Clinical and radiological features were not associated with recurrence. In a multivariate analysis, the presence of immature osteoid was a better predictor of recurrence than radiological activity (hazard ratio = 3.18, 95% CI 1.04, 9.73, P = 0.043). There was no statistically significant association between radiological activity and histological features.

Conclusions: Aneurysmal bone cysts with nodular fasciitis-like fibromyxoid areas and immature osteoid with active osteoblasts are more likely to recur. Mention of these features in histopathology reports will help to identify patients who require closer follow-up. Lesions that are apparently radiologically inactive may show fibroblastic and osteoblastic proliferation and therefore may recur.