Which of the following gene defect is associated with the development of medullary carcinoma of thyroid-
RET Proto Oncogene
Fap gene.
Rb gene
BRCA 1 gene
Thyroid carcinoma

The major types of carcinoma and their relative frequency:-

  Papillary carcinoma →  75% to 85% (most common)  
  Medullary carcinoma  → 5%
  Follicular carcinoma → 10% to 20%            
  Anaplastic carcinoma → < 5%

Most thyroid carcinomas are derived from the follicular epithelium , except for medullary carcinoma which is derived from the parafallicular or 'C' cells .
Genetic factors in different thyroid carcinoma
Papillary  →  Tyrosine kinase receptors RET or NTR K1 

          RAS mutation
          BRAF oncogene

Follicular  → RAS oncogene (NRAS, HRAS and KRAS)

                   PAX8- PPARr 1 translocation

Medullary → RET proto oncogene.
Familial medullary cancers account for most inherited cases of thyroid cancer.
Familial nonmedullary thyroid cancers (papillary and follicular) are very rare.