Desmoids

James Church

Perioperative Considerations

Genetics

Desmoid disease is the result of an abnormal proliferation of fibroblasts that happens when the Wnt/wingless signal transduction pathway is abnormally activated.
Patients with familial adenomatous polyposis (FAP) are prone to desmoid disease because APC is an integral part of the Wnt/wingless pathway, controlling the entry of beta-catenin into the nucleus.
Loss of one APC allele potentiates the loss of APC protein, which is realized by the “second hit.”
In FAP patients, it appears that the second hit, which results in the loss of APC protein, is usually surgical trauma.

Definitions

Desmoid disease in FAP includes desmoid tumors, mass lesions that appear homogeneous on computed tomography (CT) scan, and desmoid reaction.
Desmoid reaction is a flat, white, plaque-like lesion that develops on the small bowel mesentery and in the retroperitoneum (Fig. 26-1).

FIGURE 26-1 ▪ Retroperitoneal desmoid reaction: a flat, sheet-like lesion with adhesions to the mesentery of multiple loops of small bowel.
It distorts and puckers surrounding tissue and can cause small bowel and ureteric obstruction, even without there being an obvious mass lesion.
Desmoid tissue can also infiltrate the entire small bowel mesentery, compressing and weakening vessels and eroding small bowel.

Incidence and Risk with Regard to Surgical Planning

The overall incidence of desmoid tumors is 15%, while an unappreciated desmoid reaction can be found in an extra 15%, for a total incidence of 30%.
The risk of developing desmoid disease varies among patients with FAP, and assessing this risk is an important part of developing a surgical strategy.
Patients with a high risk of desmoid disease need to avoid abdominal surgery as long as possible, and when surgery is no longer avoidable, they need to have the least desmoidogenic operation.
This would be a minimally invasive colectomy with ileorectal anastomosis (see Chapters 21, 22, 23 and 24).
There is a risk factor score that is accurate in predicting development of desmoid disease (Table 26-1).

TABLE 26-1 ▪ Risk factor score for the development of desmoid disease in patients with FAP

Factor	1 point	2 points	3 points
Gender	Male		Female
Family history of desmoid disease	No	1 relative	≥2 relatives
Extracolonic manifestations of Gardner syndrome	0	1	≥2
APC mutation	5′ of codon 700	Codons 701-1399	3′ of codon 1399
FAP, familial adenomatous polyposis.

Patients with 10-12 points were at very high risk (>80%) of developing desmoid disease, while the risk for 6-9 points was 35% and that for <6 points was 5%.

Family history is the strongest of all risk factors and the site of the APC mutation the weakest, reflecting the severity of the desmoid disease more than its incidence.

Clinical Presentation

Desmoid tumors may occur within the abdomen, in the abdominal wall, or at extra-abdominal locations (Fig. 26-2).

FIGURE 26-2 ▪ Extra-abdominal desmoid located to the left of the thoracic spine.
Most patients have multiple tumors, or a combination of tumor and reaction. Symptoms and signs appear from 2 to 5 years after prophylactic colectomy.
Desmoid reaction and some desmoid tumors may be asymptomatic. They are diagnosed on CT scan or laparotomy performed for other reasons.
Desmoid tumors cause discomfort by their mass effect.
Desmoid tumors and reaction can cause a variety of complications, including bowel obstruction, ureteric obstruction, mesenteric ischemia, bowel perforation, tumor necrosis, and enterocutaneous fistula, or may just grow rapidly to overwhelm the patient. Clinical consequences include superior mesenteric artery aneurysms, bowel perforation with abscess and fistula, and bowel ischemia with stricture.

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