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Desmoid tumors and familial adenomatous polyposis: a tale of two syndromes.

As we browse through the magnificent post-Renaissance medical literature, we come across a report, written almost 300 years ago, of a condition involving multiple polyps of the colon. This article by Menzelio published in the year 1721 in Acta Medicorum Berolinensium (Fig. 1A), laid the foundation for the systematic study of the syndrome what we presently know as familial adenomatous polyposis or FAP! FAP is an autosomal dominant colon cancer predisposition syndrome characterized by 100s to 1000s of colon adenomas, and is caused by germline mutations in the adenomatous polyposis coli (APC) gene. It has been estimated to occur in about 1 in 8000 to 18,000 individuals in the general population. In about B30% of cases it has been reported to arise de novo (ie, with no family history of the syndrome). Affected individuals usually develop colon adenomas by their teens and, in the absence of treatment, there is almost a 100% risk of the adenomas progressing to colon cancer by the age of B40. Nearly a century later, in the year 1832, a new class of fibrous tumors was first described. These were later given the name ‘‘desmoides’’ [desmos (Greek)—band or tendonlike] by Müller (Fig. 1B) in 1838! Desmoid tumors are essentially fibrous tumors that present as firm, poorly circumscribed masses, and are composed of spindle cells and fibroblasts, interspersed with collagenous fibers. Although they generally do not metastasize, they can be locally invasive, and hence are sometimes also referred to as ‘‘aggressive fibromatosis.’’ The incidence of desmoid tumors in the general population is estimated to be B2 to 4/million individuals per year. They often occur as sporadic tumors and can involve the trunk, head, and neck region, and/or the extremities. They have been reported in patients ranging in age from B4 to >60 years. The etiology of these tumors remains unclear, although genetic predisposition, a history of trauma/surgery, and hormonal factors (eg, estrogen) have been implicated. The first case of a desmoid tumor occurring in association with colonic polyposis was reported by Ralph W. Nichols in 1923. It is now well known that desmoids often occur as part of the tumor spectrum of FAP. Actually, individuals with FAP have been estimated to be at >800 times higher risk for developing these tumors compared with the general population. The majority of FAP-associated desmoids tend to occur in the abdominal area (including the mesentery and the abdominal wall), although extra-abdominal sites can also be affected. They can sometimes cause compression of the surrounding vital structures, such as the small intestine, major blood vessels, and ureters, causing intestinal obstruction, ischemia, and hydronephrosis. Hence they can be a source of significant morbidity, and after prophylactic proctocolectomy, desmoids are in fact also a major cause of mortality in patients with FAP. In recent years, there have been significant advances in our understanding of the molecular mechanisms underlying both these syndromes. The key cellular defect in both FAP and sporadic desmoid tumors is an accumulation of cytoplasmic