BACKGROUND: Fluid-fluid levels (FFLs) is found in 10%-16% of giant cell tumor of bone (GCTB), and the presence of FFLs raises the suspicion of GCTB with secondary aneurysmal bone cyst (ABC), which can lead to increased intraoperative bleeding and, blurring the operative field, be associated with a risk of local recurrence. The first objective of this study is to determine whether secondary ABC is associated with a higher risk of local recurrence after curettage in patients with GCTB of the extremities. The second objective of this study is to investigate the sensitivity, specificity, positive predictive value, and negative predictive value of the presence of FFLs detected on magnetic resonance imaging (MRI) to diagnose secondary ABC associated with GCTB.
METHODS: Two hundred and eighty patients with GCTB of the extremities who underwent curettage at the authors\' institutions between 1980 and 2021 were included in this study.
RESULTS: Secondary ABC was found in 36 of 280 patients (12.9%) and local recurrence occurred in 66 of 280 patients (23.6%). Multivariate analysis showed no significant correlation between secondary ABC and local recurrence (hazard ratio [HR]: 1.87 (95% confidence interval [CI]: 1.00-3.53]; p = 0.051). Preoperative MRI revealed FFLs in 13 of 82 patients (15.9%). Sensitivity, specificity, positive predictive value, and negative predictive value of FFLs detected on preoperative MRI to diagnose secondary ABC were 36.8%, 90.5%, 53.8%, and 82.6%, respectively.
CONCLUSIONS: The results of this study showed that secondary ABC does not increase the risk of local recurrence after curettage in patients with GCTB of the extremities. Although rare, FFLs were present in patients with GCTB and half of those with FFLs detected on preoperative MRI had secondary ABC.

Fibrous dysplasia has various ways of presentation including syndromic associations and secondary changes within the lesion. We present a case of a 21-year-old female with craniofacial fibrous dysplasia, presenting with proptosis and intermittent blurring of vision due to focal fibrous dysplasia involving the frontal bone with secondary aneurysmal bone formation that was provisionally diagnosed on imaging and confirmed on histopathology. This case demonstrates the typical imaging findings of fibrous dysplasia with seldom encountered secondary aneurysmal bone cyst formation and also discusses about the pathology and management of the craniofacial fibrous dysplasia.

The purpose was to investigate the clinical features, diagnosis, treatment, and prognosis of aneurysmal bone cyst (ABC) secondary to giant cell tumors (GCT) of the extremities. Data from patients with ABC secondary to GCT of the extremities were obtained from the medical records. Clinical features, imaging findings, pathologic diagnosis, surgical methods, and prognosis were analyzed. The median age of the patients was 33 years (range 15 to 52 years) and 83.3 percent were between 20 to 40 years. The lesions were mainly located in the proximal tibia and distal femur, accounting for 63.3% (19/30). 21 patients were treated with curettage, and 9 with tumor resection. The recurrence rates of the curettage group and resection group were 52.4% and 11.1% respectively. However, the average postoperative (Musculoskeletal Tumor Society) MSTS score were 28.6±1.2 post-curettage, and 25.0±0.5 post-resection, with a significant difference between the 2 groups (P<0.01). In these relapsed patients, 10 underwent a second curettage, while 2 cases underwent a resection and there was no postoperative re-recurrence in both groups. A comprehensive analysis should be performed when making the diagnosis of ABC secondary to GCT. Although the recurrence rate is higher, curettage is still the optimal method for satisfactory joint function. If recurrence occurs after the first curettage, a second curettage should be performed.

Spinal secondary aneurysmal bone cyst (SABC) is extremely rare with few published reports available at present. Our aim is to explore the clinicopathologic features, surgical modalities and outcomes of spinal SABC.
A retrospective study of 33 patients with spinal SABC who were surgically treated in our center between 2010 and 2018 was performed. Clinical data, treatment options, complications and outcomes were analyzed.
Of the 33 patients, 12 were male and 21 were female, with a mean age of 32 years. Eleven lesions were located at the lumbar spine. The underlying lesions included giant cell tumor (GCT) (n = 20), osteoblastoma (n = 7), hemangiaoma (n = 3), fibrous dysplasia (n = 2) and osteosarcoma (n = 1). Preoperative selective arterial embolization was applied in 24 patients. All the patients were treated surgically through either subtotal resection (n = 1), piecemeal total resection (n = 21), or total en bloc resection (n = 11). Four patients experienced recurrence and one patient died during the follow-up period.
Spinal SABC is popular in the third and fourth decade of life with female predominance. GCT is the most common underlying lesion. Preoperative arterial embolization is recommended, while surgery is the mainstay of treatment for spinal SABC. En bloc resection is recommended for spinal SABCs especially when underlying tumor is aggressive or malignant.

OBJECTIVE: The epidemiology and clinicopathology of aneurysmal bone cysts (ABCs) secondary to giant cell tumors of bone (GCTBs) have been well documented in the previous literature. However, reports on whether secondary ABCs could affect the postoperative recurrence of GCTBs are rare. This study analyzed the effects of secondary ABCs and other relevant clinical factors on the postoperative recurrence of GCTBs of the extremities.
METHODS: We retrospectively analyzed 256 cases of GCTBs of the extremities that were treated surgically at our institution. Among them, there were 60 patients diagnosed with GCTBs combined with secondary ABCs and 196 patients diagnosed with simple GCTBs. Intralesional curettage and tumor resection were performed in 136 and 120 cases, respectively. Univariate analysis, Kaplan-Meier survival analysis, and multivariate regression analysis were used to assess the factors for postoperative recurrence. The follow-up period was at least 24 months.
RESULTS: The total postoperative recurrence rate was 32%. The recurrence rate in the secondary ABCs group was significantly higher than that in the simple GCTBs group (53.3% vs 25.5%, P < 0.05). Curettage was associated with a higher recurrence rate than tumor resection (42.5% vs 20%, P < 0.05). Kaplan-Meier survival analysis showed that patients with GCTBs combined with secondary ABCs and who were treated by intralesional curettage had a decreased disease-free survival rate. The hazard ratio was 2.18 (95% confidence interval [CI], 1.15-4.13) for the group of GCTB combined with ABCs ( P = 0.01) and 1.97 (95% CI, 1.22-7.50) for the curettage group ( P = 0.01), respectively. Multivariate regression analysis revealed that the presence of secondary ABCs and curettage were independent factors for recurrence of GCTBs.
CONCLUSIONS: According to the results of this study, the presence of secondary ABCs is a potential risk factor for postoperative relapse of GCTBs.

Chondroblastoma (CB) of the foot is a rare lesion. The purpose of this report was to report a large series from a single institution to analyze clinical, radiographic, and histologic characteristics; treatment; and local recurrence. We present 40 patients (30 males, 10 females; mean age 25 years) diagnosed and treated for CB of the foot from 1975 to 2012. The mean follow-up visit was 55 months (range 7 months to 11 years). Clinical presentation, histology, imaging, surgical treatment, and local recurrence were evaluated. Males were more affected than females. The main symptom was pain (100%) accompanied by swelling (35%), with median duration of 12 months. The talus (50%) and calcaneus (37.5%) were the most affected bones. All patients underwent surgery: curettage (10 cases), curettage and bone graft (15 cases), curettage and cement (13 cases), wide resection (1 case), and Chopart amputation (1 case). Ten patients (25%) had secondary aneurysmal bone cyst. One patient had local recurrence after surgery. In conclusion, patients with CB of the foot are usually older than 20 years, and males are most affected. The hindfoot is the most affected area. Surgical treatment is required, and intralesional curettage and packing with cement or graft is curative in most cases. Local recurrence in foot is lower than in other locations.

A 29-year-old woman complained of a 3-month history of left knee pain without trauma history. X-ray showed a well-defined osteolytic lesion with a sclerotic margin in the patella and magnetic resonance imaging showed T1-low and T2-high signal intensity with different fluid level. Our impression was an aneurysmal bone cyst. At surgery, the lesion was a blood-filled cystic cavity, surrounded by a gray or brownish tissue. Hemorrhagic soft tissues with recognizable bone fragments were observed. Curettage and autogenous bone graft was done. Microscopically, sheets of tumor cells were intermingled with some areas of eosinophilic chondroid matrix. The tumor cells showed oval-shaped nuclei with moderate eosinophilic cytoplasm. Several multinucleated giant cells and blood filled cystic cavities were observed. The final diagnosis was a chondroblastoma with a secondary aneurysmal bone cyst. At the post-operative 1.5-year follow-up, grafted bones were well incorporated radiographically and there were no recurrent evidence or any other abnormal symptoms.

Aneurysmal bone cyst (ABC) is a rare benign cystic lesion of the bone that composes 1-2% of the entire bone tumors. Some are idiopathic, and some occur secondary to other tumors such as giant cell tumor and chondroblastoma. In this article, we report the clinical, radiographic, and histological findings of a secondary ABC following chondroblastoma of the patella with a review of the literature.