Clinical case of familial medullary thyroid carcinoma

Medullary thyroid cancer (MTC) accounts for 5—10 % of all thyroid cancers. Most cases are sporadic (75 %), but the proportion of patients with MTC and familial medullary thyroid carcinoma (FMTC) is the highest among any hereditary cancer syndromes (appro­ximately 25 %), and this risk should be considered when evaluating a patient with MTC. In this clinical case study, case of FMTC has been elucidated. Diagnostic criteria of the disease, molecular-genetic aspects, treatment tactics and post-operative observation findings have been presented. The case study illustrates, the efficacy of genomic profiling for the identification of molecular genetic drivers of the disease and its role in ensuring proper and timely diagnosis and treatment of familial form of MTC. When planning prophylactic thyroidectomy, it is recommended to focus on the stratification of the level of RET gene mutation and the timing of prophylactic thyroidectomy as proposed by the American Thyroid Association. The use of molecular genetic investigations in clinical practice for diagnosing MTC makes it possible to objectify the genetic line of the disease in a particular biological family. The patient was found to have a pathogenic germline missense mutation c.2304 G> T (p.E768D, CM020961) in a heterozygous state, which refers to moderate risk of aggressiveness of MTC. In addition, molecular genetic test was performed for the patient's biological child, a 4-year-old girl. Pathogenic mutation was found in the CHEK2 gene, c.47OT> C (p.Ile 157 Thr) in a heterozygous state. These mutations increase the risk of developing breast cancer by 2-3 times, and by 4-5 times in the presence of family history of cancer. The presence of this mutation increases the risk of developing other types of cancers such as stomach, breast, intestinal, prostate and thyroid cancers. Timely diagnosis of FMTC allows to formulate adequate treatment strategy at the preclinical stage of the disease and can significantly improve the quality and duration of life.