Giant cell angioblastoma of bone: four new cases provide further evidence of its distinct clinical and histopathological characteristics.

Giant cell angioblastoma is a rare locally aggressive vascular neoplasm that occurs predominantly in the soft tissue of infants and children. As very few cases have been reported, the diagnostic criteria of this tumor type have not been clearly defined. The majority of earlier reported cases occurred in soft tissues, only one case being reported to arise in bone. In this study, we describe four additional cases of giant cell angioblastoma with primary presentation in bone. Two cases occurred in males: one in a 23-month-old baby and the other in an 8-year-old boy. The other two cases occurred in adult females, at an age of 37 and 56 years, respectively. The involved sites were right femur, left hip and knee joint, lumbar vertebra, left metacarpus, and phalange. The main presenting symptoms were skeletal pain (n = 3) and limping (n = 1). Clinically, three cases were suspected as tuberculosis and one case as fibrous dysplasia. Histologically, all tumors were composed of infiltrative nodules composed of angiomatous vessels surrounded by spindled-to-ovoid cells and variable numbers of histiocytoid and multinucleate giant cells. By immunohistochemistry, the angiomatous vessels were positive for endothelial markers, whereas surrounding pericytes were positive for actin. The variable histiocytoid cells and multinucleate giant cells showed a histiocytic phenotype. Follow-up revealed no signs of local recurrence or metastasis after surgery, but the follow-up periods were of limited duration. This study illustrates that giant cell angioblastoma represents a locally aggressive endothelial neoplasm characterized by nodular proliferation of small vessels with scattered multinucleate giant cells. It can occur in bone and also in adults, although very rarely.