Extragastrointestinal manifestations

Soft tissues

Tissues derived from all three germ layers are affected in FAP. As well as the endodermal lesions so far described, mesodermal lesions in the form of a fibromatosis unique to FAP, usually referred to as desmoid tumour, develop in a substantial minority of patients {315}. Desmoid tumours arise in either the retroperitoneal tissues or in the abdominal wall, often after trauma or previous surgery involving that site.

A desmoid is a mass of firm pale tissue, characteristically growing by expansion, usually rounded in shape. Desmoids begin as small scar-like foci of fibrosis in the retroperitoneal fat and, when large, typically extend around and between other structures such as the small or large bowel, ureters and major blood vessels. Histologically, these lesions are composed of sheets of elongated myofibrob-lasts, arranged in fascicles and whorls. The lesions have a dense, tough consistency and there is a variable amount of collagen. They are well vascularized and contain numerous small blood vessels that bleed profusely when incised.


Bone lesions include exostoses and endostoses. Endostoses of the mandible are found in the majority of patients {203}. They are almost always small and symptomless. Exostoses may be solitary or multiple and tend to arise in the long bones.


Dental abnormalities have been described in 11 to 80% of individuals with FAP {241}. The abnormalities may be impaction, supernumerary or absent teeth, fused roots of first and second molars or unusually long and tapered roots of posterior teeth.

In 75-80% of patients, ophthalmoscopy reveals multiple patches of congenital

Fig. 6.58 Precursor lesion of mesenteric fibromatosis (desmoid tumour) in a patient with FAP. A The white band in the mesentery resembles a fibrous adhesion. B Histology shows a band of fibromatosis in the mesenteric fat.

hypertrophy of retinal pigment epithelium (CHRPE) {280}. Ultrastructurally, they are freckle-like plaques of enlarged melanin-containing retinal epithelial cells {1466}. Their value for diagnosis is limited by inconsistency and variation between families.

Fig. 6.59 Epidermoid cyst on the dorsal surface of the hand of an FAP patient.


Epidermal cysts, usually of the face and often multiple, were first described in FAP by Gardner {565}.

Endocrine system

There is a definite but relatively slight increase in the incidence of endocrine tumours in FAP, including neoplasia of pituitary, pancreatic islets and adrenal cortex {1160}, as well as multiple endocrine neoplasia syndrome, type 2b {1500} but these are of insufficient frequency or gravity to form part of a routine screening protocol. The best documented endocrine association is papillary carcinoma of thyroid {268}, largely restricted to women {202}.

Nervous system

The concurrent presence of a brain tumour and multiple colorectal polyps constitutes Turcot syndrome. Some individuals affected in this way are victims of FAP, with a germline defect of APC. These are infants or young children who present with medulloblastoma and colorectal polyps {658}. Other individuals present later in life with a glioma, usually an astrocytoma or glioblastoma multiforme and are usually associated with hereditary non-polyposis colon cancer (HNPCC) rather than FAP {262}.

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