An Atypical Presentation of a Unicameral Bone Cyst in the Left Humerus: A Case Report.

Simple bone cysts (SBCs) are the most common osteolytic lesions in children, often leading to pathological fractures of non-weight-bearing bones. These benign tumors primarily arise in the proximal humerus, femur, or calcaneus. The cystic cavity is filled with serous or serosanguineous fluid and lined by a thin fibrovascular connective tissue membrane. The etiological factors include disturbances in bone growth, local venous obstruction, synovial origin disorders, and genetic predispositions. SBCs are most frequently observed in individuals from birth to 20 years of age. The report presented a case of a 12-year-old male patient who was admitted to the hospital with a history of a mass on his left upper arm. The mass had an acute onset and gradually progressed to its current size over three to four weeks, after which it became nonprogressive. The patient had been healthy until the age of four, after which he experienced frequent fractures of the left arm following trivial trauma. Multiple traumas led to the gradual formation of a diffuse mass over the upper part of the humerus. Radiological imaging modalities, such as X-ray and magnetic resonance imaging, are crucial in diagnosing bone cysts and evaluating their clinical conditions. Treatment can involve the injection of bone marrow or steroids into the cyst to facilitate the healing process.