Extracranial metastatic solitary fibrous tumor/hemangiopericytoma expressing G-CSF and its receptor.

Although extracranial metastases are a relatively common phenomenon in patients with solitary fibrous tumors/hemangiopericytomas (SFTs/HPCs), factors involved in the mechanism underlying tumor growth and metastasis have not been identified. We report a case of extracranial metastatic SFT/HPC synthesizing granulocyte colony-stimulating factor (G-CSF) and G-CSF receptor (G-CSFR). A 39-year-old man underwent a gross total resection of a well-circumscribed, dura-based, extracerebral primary tumor at the right frontal convexity. Neuropathologic evaluation of the tumor revealed an SFT/HPC characterized by staghorn vessels and a patternless architecture of hypercellular tumor cells, which had the eosinophilic cytoplasm and the nucleus immunoreactive for signal transducer and activator of transcription 6. He was treated with postoperative radiotherapy. He complained of fever and abdominal pain with systemic multiple metastatic tumors 10 years after the operation. The leukocyte count was 70,500/μL with 90.7% neutrophils (compared to 7400/μL at 39 years of age), and the serum G-CSF level was 283.0 pg/mL. Pathological examination of biopsy specimens of the liver and kidney tumors revealed the metastatic SFT/HPC. Immunohistochemically, G-CSF was localized in both the primary and metastatic SFT/HPC cells, whereas G-CSFR was localized only in the metastatic SFT/HPC cells. The tumors seemed to have the ability to produce G-CSF, even when G-CSF production is not clinically evident, suggesting that G-CSFR acquisition contributes to tumor growth, malignancy, and metastasis. In addition, there have been no reports showing G-CSF production in SFT/HPC cases. The influence of G-CSF is expected to be one of the factors related to SFT/HPC malignancy. Inhibitors of G-CSF could be a therapeutic agent for tumors that co-express both G-CSF and G-CSFR in an autocrine manner.