BRAF mutations typical of papillary thyroid carcinoma are more frequently detected in undifferentiated than in insular and insular-like poorly differentiated carcinomas.
Somatic mutations of the BRAF gene (BRAFV599E and BRAFK600E) were found to be closely associated with different histotypes of papillary thyroid carcinoma (PTC). The V599E mutation is highly prevalent in PTC with a papillary or mixed papillary follicular growth pattern, and the K600E mutation is apparently restricted to the follicular variant of PTC. It is usually accepted that thyroid malignancies may follow a progression path from well-differentiated to poorly differentiated (PDC) and undifferentiated (UC) carcinomas. One would expect that at least some of the less differentiated carcinomas would harbour the genetic alterations of pre-existing well-differentiated tumours. In order to find the prevalence of BRAF mutations in PDC and UC, we screened a series of 19 PDCs and 17 UCs, as well as 3 UC-derived cell lines, for both mutation types. The group of PDCs was restricted to the so-called insular and insular-like PDCs, thus excluding PTCs with solid, insular or trabecular foci of growth and PDCs displaying typical PTC nuclei. No BRAF mutations were detected in any of the 19 cases of PDC, whereas 6 of the UCs (35%) and one UC-derived cell line presented the BRAFV599E mutation. The BRAFK600E mutation was not detected in any case. We conclude that UC may progress from BRAFV599E-mutated PTC. The absence of BRAF mutations in our series of PDC supports the assumption that pure insular and insular-like PDCs are more closely related to follicular carcinoma than to PTC.
Soares
Paula
P
IPATIMUP (Institute of Molecular Pathology and Immunology of the University of Porto), R. Roberto Frias s/n, 4200 Porto, Portugal.
Trovisco
Vítor
V
Rocha
Ana Sofia
AS
Feijão
Tália
T
Rebocho
Ana Paula
AP
Fonseca
Elsa
E
Vieira de Castro
Inês
I
Cameselle-Teijeiro
José
J
Cardoso-Oliveira
Manuel
M
Sobrinho-Simões
Manuel
M
D000231:Adenocarcinoma, Papillary / Q000235:genetics* / Q000473:pathology; D002471:Cell Transformation, Neoplastic; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000032:analysis; D006801:Humans; D009154:Mutation; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics*; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000473:pathology
D004273:DNA, Neoplasm; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf