Posterior fossa solitary fibrous tumour: report of a fetal case and review of the literature.

We report a case of solitary fibrous tumour (SFT) involving the posterior fossa in a fetus of 25 weeks' gestation. SFT is a rare mesenchymal neoplasm, arising in various locations including the meninges. After disclosure of severe ventriculomegaly and posterior fossa mass measuring 45 mm in diameter, termination of pregnancy was performed in accordance with French legislation. Our neuropathological study revealed a tumour covered by meninges, with severe compression of the cerebellum and the brain stem. Microscopically, the tumour was highly cellular, made of packed small fusiform cells with branching vasculature and consistent expression of CD34. No extraneurological lesion was noted. Except cysts and vascular malformations, posterior fossa tumours have been exceptionally reported in fetuses. SFT was distinguished from hemangiopericytoma. In spite of the fact these tumours share many similarities, some criteria such as the staining pattern for CD34 instead indicated a SFT. Histology was distinctive of hemangioblastoma and primitive neuroectodermal tumour. The prognosis of solitary fibrous tumour, which is usually a benign tumour, was there worsened by the precocity of the onset and the local invasion causing disruption of the cerebellum, compression of the brain stem and severe ventriculomegaly.