RAS mutations are the predominant molecular alteration in poorly differentiated thyroid carcinomas and bear prognostic impact.
BACKGROUND
Poorly differentiated carcinomas represent an aggressive group of thyroid tumors with controversial classification placement and poorly understood pathogenesis. Molecular data in this group of tumors are extremely heterogeneous, possibly reflecting different inclusion criteria. Recently homogeneous diagnostic criteria have been proposed by our group (Turin proposal) that need to be complemented by detailed molecular characterization.


OBJECTIVE
The objective of the study was to define a comprehensive molecular typing of poorly differentiated thyroid carcinomas classified following homogeneous diagnostic criteria.


METHODS
Sixty-five cases of poorly differentiated carcinoma selected following the Turin proposal have been screened for N-, K-, H-RAS, BRAF, RET/PTC1 and 3, and PAX8/PPARgamma mutations-rearrangements using alternative techniques and in two different laboratories. Molecular data were compared with clinical pathological parameters and survival by univariate and multivariate analysis.


RESULTS
RAS mutations in codon 61 were by far the most common genetic alteration in poorly differentiated carcinomas (23% of cases), with all mutation in NRAS except one in the HRAS gene. A single BRAF mutation was found in a poorly differentiated carcinoma with a residual component of a tall cell variant of papillary carcinoma. No KRAS, RET/PTC, or PAX8/PPARgamma genetic alteration was detected. In this series, the presence of RAS mutations was a unique negative prognostic parameter at multivariate analysis.


CONCLUSIONS
The present study demonstrates that strictly classified poorly differentiated carcinomas are genetically homogeneous, RAS mutations being the almost exclusive genetic event. Moreover, the detection of RAS mutations might be clinically relevant for the prognostic stratification of these tumors.
Volante
Marco
M
Department of Clinical and Biological Sciences, San Luigi Hospital, 10043 Orbassano, Italy. marco.volante@unito.it
Rapa
Ida
I
Gandhi
Manoj
M
Bussolati
Gianni
G
Giachino
Daniela
D
Papotti
Mauro
M
Nikiforov
Yuri E
YE
D000328:Adult; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D005260:Female; D015321:Gene Rearrangement; D011905:Genes, ras / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000502:physiology*; D017354:Point Mutation; D011379:Prognosis; D012084:Renin-Angiotensin System / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013534:Survival; D016019:Survival Analysis; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000401:mortality / Q000473:pathology*
D004247:DNA