ABSTRACT
BACKGROUND: Solitary fibrous tumor (SFT) is a remarkably uncommon mesenchymal tumor. STAT6 level and a combination of clinical, pathological, and molecular features are required to arrive at a proper diagnosis. CASE SUMMARY: In this report, we present an intriguing case involving a 43-year-old woman who initially exhibited symptoms of a bleeding retroperitoneal tumor, initially resembling a gastrointestinal stromal tumor, but later confirmed as an SFT. However, a year later, what was initially believed to be a recurrence of her SFT was instead identified as a desmoid tumor. CONCLUSION: Distinguishing SFT from other tumors was pivotal. Correcting misdiagnoses of tumor type initially and of recurrence later was necessary for appropriate treatment of the correct desmoid type.