However multiple adenomas develop in the colon, its number tends to be
less than one of Familial Adenoma Polyposis or Gardner's syndrome. Also
relatively large adenomas are found, and they are thought to become malignant
more frequently. Adenomas are also recognized in the stomach,and small
intestine. As concomitant lesions other than lesions in the gastrointestinal
tract, various central nerve system tumors can be associated with this. It is
evident that the disease is hereditary. However, because the number of cases
is small, it is inconclusive whether this is recessive inheritance or dominant
inheritance, a theory of recessive inheritance is widely-accepted. Recently,
Turcot syndrome associated with brain tumors in FAP was reported, and in that
case it was a genetically-heterogenous disease and the diseases which were
arisen from APC genes produced medulloblastoma. On the other hand, that
Hereditary Non-Polyposis Colorectal Cancer (HNPCC) sometimes can produce
lesions like Turcot syndrome, and it was reported that cancers result from
hMSH-2 which is one of the genes causing HNPCC can develop
glioblastoma.