Intracranial solitary fibrous tumor/hemangiopericytoma with osteoclast-like multinucleated giant cells: Comparison with giant cell-rich solitary fibrous tumor

Aims: Intracranial solitary fibrous tumor/hemangiopericytoma (SFT/ HPC) is a mesenchymal neoplasm that typically presents in adults as a dural-based lesion. The presence of giant cells in these tumors is a rare occurrence. Materials and methods: We studied a case of intracranial SFT/HPC with unusual multinucleated, osteoclast- like giant cells and compared it to the so-called giant cell angiofibroma (i.e., giant cell-rich solitary fibrous tumor) with attention to STAT6 immunohistochemistry. Results: A 73-year-old man developed a right frontoparietal dural mass that was completely resected. Histology demonstrated a hypercellular neoplasm consisting of spindle to oval cells and scattered osteoclast-like multinucleated giant cells (MGCs), with distinctive "staghorn" blood vessels. Necrosis and brisk mitotic activity were present. The spindle cell component showed strong focal CD34 and nuclear STAT6 immunohistochemical labeling, while CD68 and CD163 were positive in MGCs. No nuclear STAT6 reactivity was detected in MGCs. By contrast, nuclear STAT6 staining was present in three cases of giant cell angiofibroma (i.e., giant-cell rich solitary fibrous tumor), both in the spindle cell component and MGCs. Conclusion: Intracranial SFT/HPC is characterized by nuclear STAT6 immunoreactivity as its soft tissue counterparts. The presence of osteoclast-like MGCs is an unusual finding in this neoplasm, which is distinct from giant cell-rich sOlitary fibrous tumor.