Time and tumor type (primary or metastatic) do not influence the detection of BRAF/NRAS mutations in formalin fixed paraffin embedded samples from melanomas.
BACKGROUND
BRAF and NRAS mutation detection is crucial for advanced melanoma treatment. Our aim was to evaluate how different characteristics from formalin-fixed paraffin-embedded (FFPE) samples, age of the block or DNA concentration could influence the success of BRAF and NRAS mutational screening.


METHODS
DNA was obtained from 144 FFPE samples (62 primary melanoma, 43 sentinel lymph nodes [SLN] and 39 metastasis). BRAF and NRAS were sequenced by Sanger sequencing.


RESULTS
Complete sequencing results were obtained from 75% (108/144) of the samples, and at least one gene was sequenced in 89% (128/144) of them. BRAF was mutated in 55% (29/53) and NRAS in 11% (5/45) of the primary melanomas sequenced. DNA concentration correlated with the tumor area used for DNA extraction (mm2) (adj p-value<0.01, r=0.73). The age of the block did not affect sequencing success. In 60% of samples kept for more than 10 years, both BRAF and NRAS were successfully sequenced.


CONCLUSIONS
Preserving sufficient tumor area in FFPE blocks is important. It is necessary to keep the FFPE blocks, no matter their age, as they are necessary to decide the best treatment for the melanoma patient.
Miriam
M
Potrony
Celia
C
Badenas
Bénédicte
B
Naerhuyzen
Paula
P
Aguilera
Joan Anton
JA
Puig-Butille
Gemma
G
Tell-Marti
Alba
A
Díaz
Cristina
C
Carrera
Llucia
L
Alos
Nicolas
N
Delahaye
Josep
J
Malvehy
Susana
S
Puig
D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000235:genetics; D005557:Formaldehyde; D020558:GTP Phosphohydrolases / Q000235:genetics*; D006801:Humans; D008545:Melanoma / Q000145:classification / Q000235:genetics* / Q000473:pathology*; D008565:Membrane Proteins / Q000235:genetics*; D009154:Mutation; D009367:Neoplasm Staging; D016612:Paraffin Embedding; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D013997:Time Factors
D004273:DNA, Neoplasm; D008565:Membrane Proteins; D005557:Formaldehyde; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D020558:GTP Phosphohydrolases; C579846:NRAS protein, human