RILIEVI T.C. ED R.M. IN UN CASO DI TUMORE A CELLULE GIGANTI DEL TAVOLATO CRANICO. CT and MR findings in a case of giant-cell tumour of the calvaria

We describe a rare case of giant-cell turnout in a 9-year-old girl, comparing the anatomopathologic features with CT and MR findings. Giant-cell tumour is a tumour of bone thought to arise from nonosteogenic connective tissue or marrow. It occurs most commonly in the 20s and 30s. The tumour is usually benign and presents varying degrees of bone destruction and in rare eases may turn malignant. The histological hallmark of the tumour is the abundance of osteoclastic multinuclear giant cells. Our patient was admitted for headache and bilateral stasis papilla due to suspect intracranial hypertension associated with diplopia. Clinical findings showed mild, probably bone swelling in the right posterior temporal lobe and the supramastoid region. CT disclosed an expanding lesion developing mainly within the endocranium and involving the whole thickness of the calvaria and diploe with thinning of the inner and outer tables of the skull. Tumour density was similar to that of the soft parts with numerous irregular calcium deposits scattered within the lesion. T1-weighted axial MR scans displayed an expanding lesion with similar signal intensity to that of soft tissues with an uneven aspect due to the presence of tiny hypointense areas T2-weighted scans demonstrated numerous areas of increased signal intensity. Histology revealed a tumour made up of a dense cell population interspersed with numerous multinuclear giant cells. Osteoid tissue was present in some areas of the tumour, probably resulting from a reactive process. Frequent bleeding had produced blood collections associated with large lacunas of blood and serum. The noteworthy features in our case are the tumour site and the patient's age. Giant-cell tumour of the skull tables must be distinguished from reparative giant-cell granuloma, brown turnout seen in patients with primary or secondary hyperparathyroidism and also from aneurysmal bone cyst and fibrous dysplasia. The comparison between anatomopathologic findings and radiological features demonstrated that the tiny images of calci- ossification within the tumour, erroneously interpreted as residual bone trabeculae, were produced by reactive osteoid tissue. The areas of increased signal intensity seen in long TR sequences and the isointense images in T1 probably correspond to the blood and serum fluid collections with a high protein content noted at anatomopathological examination, in agreement with other literature reports on giant-cell tumours of bone.