Objectives. Aneurysmal bone cyst (ABC) is a benign but locally aggressive tumor. It has several challenging features. The aim of this study is to identify challenges in the diagnosis and treatment of ABC especially in patients with unusual features. Methods. This retrospective study involved medical record review of primary ABC patients with one or more of the following features: unusual clinical presentation with a mass or a pathological fracture especially at an unusual age, rare locations, radiological findings suggesting other diagnoses especially sarcoma, and a nondiagnostic histopathology of biopsy samples. Results. 25 patients (17 males and 8 females) were included. Most patients were either younger than 10 or older than 20 years. 10 patients presented with a mass or a pathological fracture. Unusual locations include the scapula, the olecranon, the hamate, the calcaneus, and the first metatarsal bone. Extension into the epiphysis occurred in 2 patients with proximal fibula and olecranon ABCs. Two separate synchronous cysts existed in the proximal epiphysis and middiaphysis of one humerus. Radiological imaging suggested other primary diagnoses in 8 patients. Core needle biopsy was diagnostic in only 2 of 7 patients. The main treatment was intralesional resection/curettage with bone grafting. Wide resection was performed in 4 patients. Recurrence rate was 28%. Recurrence risk factors included the following: age less than 10 years, male gender, and proximal femur location. Late recurrence occurred in 3/7 patients. One patient with asymptomatic radiological recurrence showed subsequent spontaneous resolution one year later. Conclusions. This study presented multiple unusual features of ABC including: unusual age, rare locations, and nondiagnostic radiological and histopathological findings. These features can complicate the diagnosis and management. Given these features, especially with pathological fractures, a well-planned incision, the use of frozen section examination, and the application of either external fixation or plate osteosynthesis for fracture fixation can be recommended.

BackgroundSynovial sarcoma is a rare soft tissue sarcoma which most commonly affects the extremities of young adults. Axilla involvement by this sarcoma is very rare especially with involvement of the brachial plexus. This combination adds to the challenge in approaching such tumors which might significantly affect survival and function.Case presentationHerein, we present a 48-year-old female patient who presented with an isolated painless lump in her right axilla. Initially, her workup, looking for possible breast cancer, included fine-needle aspiration (FNA) which did not provide the diagnosis. Core-needle biopsy, performed later, revealed monophasic synovial sarcoma. Her workup studies revealed no metastasis. Then, through extensile deltopectoral approach, the tumor was dissected out from within the brachial plexus. Ulnar nerve was sacrificed in order not to compromise the surgical margins which were confirmed tumor free by final pathology. The patient did not receive chemotherapy or radiation upon consultations with medical and radiation oncology teams. Her follow-up revealed no tumor recurrence with no restriction of her right shoulder motion.ConclusionOur case report represents a very rare occurrence of synovial sarcoma in the axilla with involvement of the brachial plexus. When clinical and radiological findings are suggestive of soft tissue sarcoma of the axilla, we recommend getting core-needle biopsy rather than fine-needle aspiration for earlier diagnosis. Early referral and multidisciplinary approach may contribute to better management.