From: Multimodality imaging features of desmoid tumors: a head-to-toe spectrum
• ~ 0.03% of all neoplasms; < 3% of all soft tissue tumors.
• 30% of familial adenomatous polyposis (FAP) patients have desmoid-type fibromatosis (also called Gardner syndrome); 7.5–16% of patients with fibromatosis have FAP.
• Mean age: 36–42 years.
• Female predominance from puberty to age 40; younger and older patients have M:F = ~ 1:1.
• Male predominance in FAP of 3:1.
• 37–50% occur in the abdominal region.
• Shoulder girdle, chest wall, and inguinal regions are the most prevalent extra-abdominal sites.
o In FAP: majority (51–67%) are intra-abdominal or in the abdominal wall.
o Sporadic: extra-abdominal are more common.
• Abdominal wall is the prevalent site in premenopausal and pregnant women.
• CTNNB1 and APC gene mutations (up to 89% of cases).
• High estrogen states and positive trauma history can lead to activation of the Wnt/β-catenin pathway.
• Local recurrence in 20–30%.
• Margin status critical for local recurrence in primary tumors but not significant in recurrent presentations.
• CTNNB1 S45F mutation associated with significantly increased risk of recurrence.