Osteoid osteoma is a benign osteoblastic tumor that consists of a central nidus composed of bony trabeculae (seen in the right two-thirds of this image) surrounded by a zone of sclerotic bone (left one-third of the image). The nidus and surrounding bone are sharply demarcated from each other. The osteoid trabeculae are separated by vascular fibrous connective tissue. The lesion bears resemblance to an osteoblastoma. Indeed, some authors arbitrarily label all such lesions greater than 2 cm as osteoblastomas. The tumor has male predilection (M:F=3:1) and is more common in younger individuals.