Sellar Solitary Fibrous Tumor Mimicking Pituitary Adenoma: Diagnostic Pitfalls and Radiological–Pathological Correlation

Background/Objectives: Sellar solitary fibrous tumors (SFTs) are exceptionally rare mesenchymal neoplasms that frequently mimic non-functioning pituitary adenomas both clinically and radiologically. Because of their nonspecific imaging characteristics, accurate preoperative diagnosis remains challenging and often requires histopathological and immunohistochemical confirmation. Nuclear STAT6 expression has become a key diagnostic marker for this entity. Methods: We present a case-based diagnostic analysis of a high-grade (WHO grade 3) sellar SFT initially misdiagnosed as a pituitary adenoma. Clinical, radiological, intraoperative, and histopathological findings were systematically evaluated and correlated. In addition, previously reported sellar SFT cases were reviewed to identify recurring diagnostic patterns and pitfalls. Results: A 65-year-old male presented with headache, progressive visual impairment, and hypopituitarism. Magnetic resonance imaging demonstrated a heterogeneously enhancing sellar mass with suprasellar extension and cavernous sinus involvement, leading to a presumptive diagnosis of pituitary adenoma. Intraoperatively, the lesion was markedly hypervascular and fibrous, raising suspicion for an alternative diagnosis. Histopathological examination revealed a spindle-cell neoplasm with a hemangiopericytoma-like vascular pattern, increased mitotic activity, and strong nuclear STAT6 positivity, confirming a WHO grade 3 SFT. Literature analysis showed that most reported sellar SFTs share overlapping MRI features with pituitary adenomas and are frequently misdiagnosed preoperatively. Conclusions: Sellar SFT should be considered in the differential diagnosis of atypical sellar lesions, particularly when imaging findings are inconclusive and intraoperative features suggest a hypervascular and fibrous tumor. Radiological–pathological correlation, including STAT6 immunohistochemistry, is critical for accurate diagnosis. Increased awareness of these diagnostic pitfalls may improve recognition of this rare entity and guide surgical and pathological decision-making.