Fourteen FNMTCs in patients from seven families were analyzed in terms of involvement of the four susceptibility loci, and 63 thyroid cancer tumors [FNMTC (29) and NMTC (34)] were evaluated for the occurrence of mutations in BRAF, and H-, N-, and K-RAS, using polymerase chain reaction, single-strand conformation polymorphism (PCR-SSCP) analysis, and direct sequencing.