Familial adenomatous polyposis and desmoid tumors

Familial adenomatous polyposis (FAP) is a hereditary condition transmitted in an autosomal dominant fashion, which is characterized by the appearance of numerous adenomatous polyps in the colon. This condition results from mutation of the APC gene and accounts for 1% of cases of colorectal cancer. FAP is frequently associated with extracolonic manifestations: desmoid tumors, osteomas, pigmented lesions of the retina, adenomas of the upper gastrointestinal tract, and epidermoid cysts, as well as gastric, thyroid, suprarenal, and central nervous system cancer. The desmoid tumor (DT) is a benign neoplasm that occurs in 10%–20% of the patients with FAP. It originates from fascial or muscle-aponeurotic structures that foster fibroblast proliferation. DTs occur more frequently in the intraabdominal region or the abdominal wall, although they can also be detected in extra-abdominal areas. It is a rare type of tumor, representing 0.03% of neoplasms. Compared with the general population, a patient with FAP is at an 852-fold increased risk of developing a DT. Although benign from a histological viewpoint, a DT can display aggressive biological behavior characterized by infiltrative growth and a high recurrence rate after resection. DTs represent the second most common cause of death in patients with FAP.