Patient had left shoulder pain for 1 year. A, Anteroposterior radiograph of left shoulder reveals lytic lesion in proximal left humerus extending across open physis. B, CT scan shows calcification of lesion. C and D, MR images show fluid-fluid level. Incision biopsy confirmed diagnosis of chondroblastoma with secondary aneurysmal bone cyst. E, Anteroposterior radiograph after curettage and bone grafting. F, Typical microscopic appearance of chondroblastoma.