Recurring osteoblastoma initially presenting as a typical osteoid osteoma

Two patients each underwent inadequate excision of an osteoid osteoma and some months later developed a large tumor in the same location showing the radiographical and histological features of osteoblastoma. This rare occurrence again suggests that osteoid osteoma and osteoblastoma are closely connected benign neoplasms. Indeed some authors in the past have suggested classification as a single tumor showing different clinical and radiographical patterns.Supported by: Grant n 88.01124.44, Italian National Council of Researches, Special Project Oncology. A.I.R.C. (Italian Association for Cancer Research). Regione Emilia-Romagna, law n 1970 of May 13th, 1986. Istituto Ortopedico Rizzoli Research Funds. Interdepartmental Center for Cancer Research G. Prodi of the University of Bologna