Epithelioid osteoblastoma: A histopathological dilemma between juvenile ossifying fibroma and low-grade osteosarcoma

A case of epithelioid osteoblastoma of the thoracic vertebra in a 12-year-old male: a case report and review of literature

Introduction and importance

Osteoblastoma (OB) is a rare benign bone tumor, representing less than 1% of all bone neoplasms. In contrast to the typical OB, a smaller subset known as 'epithelioid osteoblastoma (EO)' exhibits a distinctive inclination for local invasion and recurrence. This rare variant can pose diagnostic challenges, particularly due to its unclear clinical and radiological presentation.

Case presentation

This study details a clinical case of a 12-year-old boy experiencing pain from a lytic bone tumor located in the thoracic vertebrae (T3-T4), initially suggesting malignancy. Following extensive curettage, histopathological analysis confirmed the diagnosis of EO through immunohistochemical staining. Subsequent follow-up at 3 months revealed the absence of no pain or recurrence of the lesion.

Clinical discussion

Distinguishing EO from a malignant tumor requires a multidisciplinary approach, considering clinical, radiographic, and histological features that differentiate the two entities.

Conclusion

The goal of this case presentation is to increase awareness regarding this recurrent tumor variant, which poses diagnostic challenges, particularly in distinguishing it from malignant tumors, including osteosarcoma.

Clinicopathologic study of 6 cases of epithelioid osteoblastoma of the jaws with immunoexpression analysis of FOS and FOSB

OBJECTIVE

The aim of this study was to describe the clinicopathologic features of a series of gnathic epithelioid osteoblastomas. As high levels of Proto-oncogene c-Fos proteins resulting from FOS-FOSB translocation were recently demonstrated in osteoblastomas, we also evaluated the immunoexpression of these proteins.

STUDY DESIGN

Records of all cases of epithelioid osteoblastoma of the jaws were retrieved from oral pathology services, and their clinicopathologic and immunohistochemical data were collected. Immunohistochemistry was also performed by using anti-FOS and anti-FOSB antibodies.

RESULTS

Six cases of epithelioid osteoblastomas were obtained, 4 in men and 2 in women, and they were mainly located in the posterior body of the mandible (n = 4). Radiographically, the tumors showed mixed radiolucent and radiopaque images, most with poorly defined margins. Microscopically, large epithelioid cells with eccentrically located nuclei predominated among osteoid and immature bone trabeculae. Sharp delineation from adjacent normal bone was observed in all cases. FOS immunostaining was diffuse and strong in the cytoplasm and nucleus of neoplastic cells in all cases, whereas FOSB was only focally positive, with few epithelioid osteoblasts showing nuclear staining.

CONCLUSIONS

Although epithelioid osteoblastomas of the jaws are locally aggressive, widespread metastasis does not occur, and, as with conventional osteoblastomas, there is wide expression of the FOS protein.