Meningeal hemangiopericytomas and hemangiopericytoma/solitary fibrous tumors of extracranial soft tissues: a comparison

The current World Health Organization (WHO) classification of central nervous system tumors lists meningeal hemangiopericytomas (HPC) and meningeal solitary fibrous tumors (SFT) as separate entities. On the contrary, SFT and HPC of soft tissues are regarded in the WHO soft tissue fascicle as features of the same entity. The clinical data, histology, and immunohistochemistry of 18 cases of meningeal HPC and 12 cases of peripheral soft tissue HPC-SFT were compared. Both intracranial and soft tissue lesions had significant similarities that included staghorn vasculature, necrotic areas, cytologic atypia, and positivities for CD99, collagen IV, and reticulin. Nevertheless, intracranial tumors were more cellular than HPC-SFT of soft tissues and had fewer collagen bands. Meningeal HPC in addition had more mitoses, higher Ki67 index, stained less intensely for CD34 and B-cell lymphoma 2 (BCL2) than HPC-SFT of soft tissues. Meningeal HPCs recurred in 13 out of 14 cases (92.9%). One of the patients died in the postoperative period for a recurrent lesion 5 years after the diagnosis, and another patient developed an extracranial metastasis 13 years after surgery. None of the six cases of HPC-SFT of soft tissues available for follow-up recurred. Both meningeal and soft tissue tumors appear to represent different features of the same entity. A more aggressive phenotype of the tumor together with incomplete surgical resection of intracranial lesions might explain the noticeable clinical difference between HPC of the meninges and HPC-SFT of soft tissues.