Cancer itself cannot be inherited but sometimes faulty genes that increase the risk of developing cancer can be passed on from parent to child.
Most medullary thyroid cancers (about 75%) are not due to inheriting a faulty gene. These are called sporadic cancers. But some (about 25%) are caused by certain conditions that can be passed on in the family.
The inherited conditions are
- Multiple endocrine neoplasia 2 (MEN2)
- Familial medullary thyroid cancer (familial MTC)
The faulty gene that causes medullary thyroid cancer is called the RET proto-oncogene. Abnormal RET genes are most often inherited as part of the condition MEN2.
There are two types of MEN2. Both types increase the risk of medullary cancers of the thyroid gland.
A small number of families are prone to develop medullary thyroid cancer but don't have any symptoms of MEN2. This is called familial medullary thyroid cancer (familial MTC)
Medullary cancers linked with MEN2 tend to affect people at a younger age than sporadic cancers. In MEN2A medullary thyroid cancer tends to affect adults in their 30s or younger. In MEN2B the cancer also occurs at an early age and may develop in childhood. Sporadic and familial medullary thyroid cancers tend to develop later and are more common between the ages of 40 to 55.
If a person is diagnosed with medullary thyroid cancer, their doctor will arrange for them to have genetic testing. If this shows that the cause is a faulty RET gene, other family members will be offered genetic testing.
References
- Guidelines for the management of thyroid cancer in adults. British Thyroid Association. Royal College of Physicians 2002.