Unusual Orbital-Cranial Metastasis of a Malignant Solitary Fibrous Tumor

Background: Malignant solitary fibrous tumors (MSFT) are uncommon spindle cell neoplasms thought to arise from mesenchymal lineages. While historically considered pleural cavity tumors, solitary fibrous tumors have been described throughout the body—not only as primary tumors, but also as both synchronous and delayed metastases. We describe an unusual MSFT, originating within the orbital compartment and metastasizing to the calvarium and liver.

Methods: Case report.

Results: A 59-year-old man had a history of MSFT of the left eye status post enucleation in 2008, complicated by hepatic metastases, status post stereotactic body radiation therapy, surgical resection, and intraoperative radiofrequency ablation in 2014 (Fig. 1). One year later, the patient presented with several weeks of progressive weakness of the left lower extremity in the setting of a subacute growing calvarial mass the patient had attributed to unresolved sequelae of a minor head trauma. MRI of the brain demonstrated a 6.7cm × 5cm, heterogeneously contrast-enhancing, right parietal transcalvarial mass with extracranial, intracranial extraaxial, and intracranial intraaxial components, as well as MRV-confirmed occlusion of the superior sagittal sinus (Fig. 2). Ultrasound-guided biopsy confirmed MSFT, and the patient subsequently underwent a biparietal craniotomy for tumor resection. Intraoperatively, a large, hemorrhagic, encapsulated mass was observed intra- and extracranially, with obvious connection through an emissary venous passage, and no involvement of the galea (Fig. 3). The tumor was extensively resected—with ligation and resection of the involved sinus—and the calvarium was reconstructed with titanium mesh (Fig. 4). Postoperatively, the patient developed a bilateral supplementary motor area syndrome, characterized mainly by lower extremity weakness. His condition gradually ameliorated and he was ultimately discharged to inpatient rehabilitation with significantly improved neurologic function as compared with his immediate post-operative state. Pathologic analysis confirmed metastatic solitary fibrous tumor, with positive immunohistochemical staining for synaptophysin, STAT6, chromogranin, cytokeratin AE1/AE3, CAM 5.2, and OSCAR (Fig. 5). Of particular interest was the high expression level of STAT6, as oncogenic transformation of this transcription factor is a frequent occurrence in MSFTs. Follow-up plans include medical and radiation oncology consultations, with consideration for both radiation and VEGF-R tyrosine kinase inhibitor (sunitinib) therapies.

Conclusion: This is the first reported case of a primary orbital MSFT with metachronous hepatic and cranial metastases. The clinical history demonstrates the potential for this rare cancer to progress rapidly and insidiously, prompting a possible recommendation for increased surveillance, particularly within the cranial compartment. Further, it illustrates the capacity for significant tumor investment within the central nervous system and its vasculature at the tumor interface, which may place patients at increased risk of postoperative complications. Additional study is required to definitively characterize the natural history and outcomes of these unique and unusual tumors.