Intracranial myopericytoma: a tumour in a rare location.

A 49-year-old female with history of headache, nausea and vomiting with some weeks of evolution, without neurological symptoms. Radiology revealed an expansive lesion near the inferior vermix and cerebellar tonsils, with heterogeneous gadolinium uptake and mass effect on the fourth ventricle, representing a probable extraventricular origin for the lesion. Pathological examination showed a proliferation of oval/spindle cell proliferation with eosinophil cytoplasm and small and monotonous nuclei, without mitoses. The cells had a concentric growth, surrounding thin-walled blood vessels with foci of stromal myxoid degeneration and whorled pattern. The vessels had a haemangiopericytoma pattern and were lined by non-atypical endothelial cells. The tumorous cells expressed vimentin, alpha-smooth actin and heavy-chain caldesmon and were negative for epithelial membrane antigen, protein S100, HMB45, CD34, calponin and desmin, thus providing the final diagnosis of intracranial myopericytoma.