Epithelioid multinodular osteoblastoma: a clinicopathologic analysis of 26 cases

We describe the clinical, radiologic, and pathologic features of 26 osteoblastomas with a multinodular growth pattern (defined as multiple nidi in a single tumor) and primarily epithelioid-appearing cells. Clinical information and histologic slides for all 26 patients and radiologic studies for 9 were examined. Follow-up information was obtained from medical charts at our institution and from correspondence with pathologists who submitted cases in consultation. Of the 23 patients with osteoblastoma whose sex had been recorded, 18 were male and 5 were female (median age, 17.8 y). The most common site was the jawbones, although long bones were also involved. Radiologic studies suggested a benign lesion in 5 patients, a malignant lesion in 2, and indeterminate features in 2. Histologically, the tumors appeared to be multiple nodules of epithelioid cells, most with a lacy, blue-bone matrix. Frequently, there were sheets of cells with no matrix. Follow-up information was obtained for 14 of the 23 patients. One patient died in an automobile accident; all others were alive as long as 29 years after treatment. Epithelioid osteoblastomas mimic osteosarcoma because of similar cellularity and cytologic features. Although follow-up is limited, we are cautiously optimistic that these are benign lesions.