Inherited Medullary Thyroid Cancer: In inherited medullary thyroid cancer prospective family screening is essential due to the 90 to 95% penetrance of the disease. Inherited MTC is usually present by the third decade of life. Inherited syndromes of medullary thyroid cancer are all transmitted in an autosomal dominant form. The mutation is detected in the tyrosine kinase proto-oncogene RET and can be identified in 98% of affected family members with appropriate screening. Also know: 6% of patients with sporadic medullary thyroid cancer carry a germline RET mutation. Genetic testing should, thus, be offered to all patients with newly diagnosed apparent sporadic disease. MEN 2B patients tend to exhibit more locally aggressive MTC , and screening with RET testing is recommended at age 6 months or prior; for familial MTC and MEN 2A screening is recommended by 5 years of age. Other oncogenes: FOS - Overexpression is seen in osteosarcomas BRAF - Point mutation seen in melanoma, lung, colorectal carcinoma WNT1 - Amplification is seen in retinoblastoma Ref: 1. Busaidy N.L., Habra M.A., Vassilopoulou-Sellin R. (2011). Chapter 38. Endocrine Malignancies. In H.M. Kantarjian, R.A. Wolff, C.A. Koller (Eds), The MD Anderson Manual of Medical Oncology, 2e. 2. Morin P.J., Trent J.M., Collins F.S., Vogelstein B. (2012). Chapter 83. Cancer Genetics. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e