BACKGROUND: Screening medullary thyroid carcinomas (MTCs) for rearranged during 
transfection (RET) mutations becomes increasingly important for clinical 
assessment of the disease. The role of mutations in other genes including RAS 
(i.e. HRAS, KRAS, and NRAS), v-raf murine sarcoma viral oncogene homolog B1 
(BRAF), v-akt murine thymoma viral oncogene homolog 1 (AKT1), and CTNNB1 
(β-catenin) is unknown or not fully explored yet for this disease.
MATERIALS AND METHODS: Formalin-fixed and paraffin-embedded (FFPE) material was 
the primary source for screening 13 sporadic and inherited MTCs and matched 
non-tumor specimens. Multiplex PCR was included in the PCR protocol. Sequence 
analysis encompassed mutational hotspot regions in RET exons 5, 8, 10, 11, and 
13 to 16; HRAS exons 1 and 2; KRAS exons 1 and 2; NRAS exons 1 and 2; BRAF exon 
15; AKT1 exon 2, and CTNNB1 exon 3.
RESULTS: We identified RET mutations in seven of 13 MTCs: five RET-positive 
cases revealed a mutation in exon 16 (M918T) and two a mutation in exon 10 
(C618S and C620S). In four of the RET-positive cases, the mutation was 
inherited, out of which three were reportedly associated with a multiple 
endocrine neoplasia type 2 (MEN2) syndrome, i.e. MEN2A (C618S), MEN2A/familial 
MTC (FMTC) (C620S), and MEN2B (M918T). These cases reflect the known MEN2 
genotype-phenotype correlation. Three of the five stage IVc MTCs were inherited 
RET-positive cases. Mutational screening in HRAS, KRAS, NRAS, BRAF, AKT1, and 
CTNNB1 disclosed one sporadic RET-negative MTC (stage III) with mutation in HRAS 
codon 13 (G13R).
CONCLUSION: Our study supports the clinical relevance of screening MTC patients 
for RET mutations. The role of RAS mutations, in particular HRAS mutations, in 
sporadic RET-negative MTC has not been fully explored yet. Mutations in BRAF, 
AKT1, and CTNNB1 are likely not to play a role in MTC.