Osteoblastomas are rare bone-producing neoplasms that generally occur in the young and can be misdiagnosed as an osteosarcoma if correlation with clinical history, radiology, and histology is not carefully considered or if the several variants of osteoblastoma are not recognized. These variants lie on a morphologic spectrum between conventional osteoblastoma and osteosarcoma. Aggressive osteoblastoma is one such subtype. As the name implies, the histologic features of aggressive osteoblastoma may appear malignant, and its biologic behavior may separate it from conventional osteoblastoma. We report a case of aggressive osteoblastoma occurring in the femoral diaphysis of a 12-year-old girl; this osetoblastoma was dyssynchronous from the radiologic appearance and a diagnostic challenge. Cytogenetic evaluation of the neoplasm revealed a pseudodiploid clone with a balanced translocation involving chromosomes 4, 7, and 14. Using the premise that cytogenetics might be useful as a diagnostic tool for a more specific classification, we reviewed the literature in order to compare our findings with known chromosomal aberrations. © The Author(s) 2010.