Context: Solitary fibrous tumor is a distinct neoplasm, rarely recognized in extrathoracic sites.
Case report: The article reports a new case in the retroperitoneum in a 55 year-old man, who presented with urinary symptoms. Tumor was completely excised, and the solitary fibrous tumor was diagnosed after pathologic examination and immunohistochemistry. The patient has remained free of disease for five years since surgery.
Conclusion: An uncommon variant of retroperitoneal solitary fibrous tumor with giant multinucleated cells was documented in the study.
Keywords: histopathology; retroperitoneum; solitary fibrous tumor.