Screening for Patients with Abdominal Wall Desmoid Tumors
A patient with an abdominal wall desmoid tumor should be screened for colon polyps due to the strong association between desmoid tumors and Familial Adenomatous Polyposis (FAP). 1
Association Between Desmoid Tumors and FAP
- Desmoid tumors can occur in up to 26% of patients with Familial Adenomatous Polyposis (FAP), making them a significant extraintestinal manifestation of this hereditary syndrome 2
- Abdominal wall desmoid tumors specifically show a strong association with FAP, with patients having an 18.9 times higher odds of having FAP compared to those with extra-abdominal desmoid tumors 3
- Desmoid tumors in FAP patients typically develop after the diagnosis of FAP, but they can sometimes be the presenting feature before gastrointestinal manifestations appear 4
Risk Assessment and Screening Recommendations
- All patients with abdominal wall desmoid tumors should undergo colonoscopy to screen for colorectal polyps, as this may lead to early diagnosis of FAP 1
- The Chinese Society of Clinical Oncology (CSCO) guidelines specifically state that patients with abdominal desmoid tumors should be alerted to the possibility of FAP and recommended for FAP genetic screening 1
- British Society of Gastroenterology guidelines emphasize that desmoid disease is a significant complication of FAP and recommend genetic testing for patients with desmoid tumors 1
Genetic Testing Considerations
- Genetic testing for APC mutations should be considered in all patients with abdominal wall desmoid tumors, even without a family history of FAP 1
- Mutations in specific regions of the APC gene (between codons 543-713 and 1310-2011) are associated with an increased risk for desmoid tumors 1
- A positive family history of desmoid tumors, previous abdominal surgery, and APC mutation are independent risk factors for desmoid tumor development 4
Surveillance Protocol for Patients with Confirmed FAP
If FAP is diagnosed following screening:
- Colonoscopic surveillance should commence at age 12-14 years in confirmed FAP patients 1
- Upper GI surveillance should begin at age 25 years 1
- Annual thyroid examinations should begin in the late teen years 1
- Regular physical examination and consideration of baseline abdominal imaging for desmoid disease surveillance 1
Clinical Pearls and Pitfalls
- Not all desmoid tumors are associated with FAP - sporadic cases are more common, but the incidence of FAP-related desmoid tumors is significantly higher in the FAP population 3
- A study showed that routine colonoscopy in desmoid tumor patients without gastrointestinal symptoms had low diagnostic yield for FAP, but this should not deter screening in patients with abdominal wall desmoids specifically, which have a stronger association 2
- Desmoid tumors and duodenal polyps are now the leading causes of death in FAP patients who have undergone prophylactic colectomy, highlighting the importance of comprehensive screening 5, 6
- The answer is (b) colon polyps, as screening for the other listed conditions (lung cancer, breast cancer, medullary thyroid carcinoma, and pancreatic cancer) is not routinely recommended for patients with isolated desmoid tumors 1