Osteoblastomas are composed of anastomosing bony trabeculae separated by loose fibrovascular stroma. The mineralized central portion of this osteoblastoma resembles the nidus of an osteoid osteoma. Many cases have composite features of both. In such cases, some authors arbitrarily label lesions larger than 1.5 cm as osteoblastoma. Osteoblastomas have been referred to in the past as giant osteoid osteomas - a term that hints at histologic similarities between the two while at the same time referring to the larger size of osteoblastomas.