Giant cell reparative granuloma of the cranial vault: exceptional bone lesion.

Giant cell reparative granuloma (GCRG) is an uncommon nonneoplastic lesion of bone. It is even rarer in the bones of the skull, particularly in the calvarial bones. Originally considered to be peculiar to the jawbones, GCRG has been described in some other locations, such as the short tubular bones of the hand and the facial (paranasal) bones. Only one GCRG has been found in the skull, this one in the temporal bone. The authors were unable to find a report of such a lesion in the bones of the calvarium. The etiology of GCRG is unknown, but it is believed to result from a traumatic intraosseous hemorrhage or periosteal reaction. A GCRG was diagnosed in a 31-month-old male infant who presented with a nonpainful, slow-growing, right frontal swelling, apparently related to a head contusion that had occurred 21 months earlier. The lesion was removed surgically. The main differential diagnosis is giant cell tumor.