A 14-year-old male patient had swelling in his right leg with intermittent pain for 1 year. The swelling of the lower leg was severe after exercise and could be relieved by rest. The previous month, he was treated at an external hospital, and the plain film radiography showed a lesion of the right tibia, so he came to our hospital for treatment. Physical examination: both lower limbs were equal in length, and obvious swelling or tenderness was not palpated in the right lower leg. The movement of both lower limbs and the muscle strength were normal. Plain radiography: the cortical expansive bone destruction of the anterior edge of the right upper tibia was irregular and lobulated, and the sclerotic edge could be seen. The long axis of the lesion was consistent with the tibia, with a maximum cross-sectional area of 2.1 x 1.9 cm and a length of approximately 7.5 cm, with no obvious periosteal reaction and no definite soft tissue mass. Computed tomography (CT): the lesion showed an eccentric polycystic expansive lucency area, and the bone cortex was expanded and thinned. Cortical interruption could be seen on some levels, and a small local lamellar periosteal reaction was observed in some parts. The lesion was associated with pathological fracture. Magnetic resonance imaging (MRI): the lesion of the upper right tibia showed a low signal on T1-weighted imaging (T1WI), a high signal on T2-weighted imaging (T2WI), and a high signal on diffusion-weighted imaging (DWI). The lesion showed significant enhancement on the postcontrast MRI scan. The preoperative imaging diagnosis was OFD of the upper right tibia with pathological fracture. After admission, the patient underwent tumor resection of the right tibia, free transplantation of the left fibula, and internal fixation. During the operation, the lesion was found to be located in the anterolateral bone cortex of the right tibia, and the tumor was white, flexible, and bleeding. The patient had good tolerance to the surgery with stable intraoperative condition. After resection of the tumor, the wound recovered well, the vital signs were stable, and activity was normal. Pathological examination showed a small amount of hyperplastic fibrous tissue and irregular woven bone and osteoblasts, in which scattered nest-like epithelial cells were seen. The immunohistochemistry results showed Ki-67 (+1%), SATB2 (+), CK19 (1+), AE1/AE3 (1+), CK18 (-), EMA (-), P63 (1+), S-100 (-), MDM2 (2+), SMA (-), and beta-catenin (2+, cytoplasm) ( Figure 1 ). The patient was recommended to be closely followed up and observed after the operation, avoiding weight bearing to prevent the aggravation of pathological fracture. The patient has been followed up for more than a year with no recurrence or distant metastasis.