A 16-year-old boy presented at the emergency room after he fell on his left shoulder while playing American football. Plain radiographs showed a pathological fracture through a well- defined expansile radiolucent lesion within the proximal meta-diaphysis of the left humerus (Fig. A). The lesion caused cortical thinning and contained multiple linear cortical fragments within the central part of the lesion (arrows in Fig. A). Based on the age, location and the plain radiographic characteristics (“fallen fragment sign”), the diagnosis of a solitary bone cyst (SBC) was suggested.