Table 2.

Extracolonic Manifestations of APC Gene Mutations

	Incidence (%)	Significance
Duodenal adenomas	80–90	12% risk of malignancy
Gastric hamartomas	50–70	Must exclude gastric adenoma
Desmoids	12–38	27% risk of complications
Hepatoblastoma	1	Most common before age 2 years
Osteomas	80	Usually less than 1 cm in size
Congenital hypertrophy of the retinal pigment epithelium (CHRPE)	80	Marker for screening purposes