Retroperitoneal Solitary Fibrous Tumor: A "Patternless" Tumor

Area of Science:

• Oncology
• Pathology
• Surgical Oncology

Background:

• Solitary fibrous tumors (SFTs) are uncommon mesenchymal neoplasms, typically originating in the pleura.
• Retroperitoneal SFTs are exceptionally rare, posing diagnostic difficulties due to their nonspecific presentation and challenging histopathology.

Observation:

• A 55-year-old female presented with nonspecific abdominal pain, revealing a retroperitoneal/pelvic mass near the upper rectum.
• The pelvic tumor was surgically resected with clear margins, utilizing a total mesenteric excision surgical plane.

Findings:

• Histopathological examination confirmed the diagnosis of solitary fibrous tumor.
• Microscopic features included a "patternless pattern," storiform arrangement of spindle cells, hemangiopericytoma-like vascularity, and increased vascularity.

Implications:

• This case contributes to the limited literature on retroperitoneal SFTs, with fewer than 100 reported instances.
• Surgical resection is the primary treatment modality for SFTs, associated with generally low recurrence rates.