Why and how immunohistochemistry should now be used to screen for the BRAFV600E status in metastatic melanoma? The experience of a single institution (LCEP, Nice, France)

Abstract

This study showed that VE1 IHC should be a substitute for molecular biology in the initial assessment of the BRAFV600E status in MPP. This methodology needs to be set up in pathology laboratories in accordance with quality control/quality assurance accreditation procedures. Under these strict conditions the question is to know if BRAFV600E-IHC can serve not only as a prescreening tool, but also as a stand-alone test (at least in cases displaying an unequivocally staining pattern) as well as an alternative predictive test for samples for which the molecular biology failed.

Standardized fixation process is crucial to permit molecular analyses in formalin-fixed and paraffin-embedded melanoma samples

“…In their study, Potrony et al encountered a DNA extraction failure in 10% of melanoma samples [1]. This rate of inconclusive samples is also encountered in other studies dedicated to mutational screening in melanoma samples [2,3].In our experience, we recently lead two successive studies to evaluate BRAF and NRAS mutational status using pyrosequencing and BRAFV600E and NRASQ61R mutation specific immunohistochemistry in melanoma samples. We analyzed, on the one hand, retrospectively 142 FFPE samples from 2003 to 2013 [4].…”

“…In their study, Potrony et al encountered a DNA extraction failure in 10% of melanoma samples [1]. This rate of inconclusive samples is also encountered in other studies dedicated to mutational screening in melanoma samples [2,3].…”

“…Additional criteria as low percentages of tumor cells in some samples are also partially responsible of these inconclusive analyses but a few samples still do not allow correct DNA extraction. Mutation specific immunohistochemistry could help to interpret these challenging and molecularly inconclusive samples searching for the mutant proteins instead of the mutations at the DNA level [2][3][4][5][6].…”

“…Additional criteria as low percentages of tumor cells in some samples are also partially responsible of these inconclusive analyses but a few samples still do not allow correct DNA extraction. Mutation specific immunohistochemistry could help to interpret these challenging and molecularly inconclusive samples searching for the mutant proteins instead of the mutations at the DNA level [2][3][4][5][6].In this way, we agree with Potrony et al that the time of conservation of the FFPE samples does not greatly influence the success of DNA analyses but we also want to remind the reader that the fixation process is a crucial step in the management of melanoma and, in a larger way, of every solid tumor sample to allow further molecular analyses. Four percent buffered neutral formalin fixation during about 24 h seems to be an adequate fixation process to allow histopathological, immunohistochemical and also additional DNA-sequencing analyses.…”

BRAF V600 mutation detection in melanoma: a comparison of two laboratory testing methods

“…Recent publications examining the use of monoclonal antibodies on FFPE tissue for the detection of BRAF mutation have shown a high sensitivity and specificity for the detection of the BRAF V600E mutation when compared with PCR 41–50. Performing IHC for mutational analysis has the advantage of an improved turnaround time (theoretically a result is possible within hours), in addition to being a cost-effective alternative to PCR 46. Smaller tumour samples/biopsies are also more suitable for IHC analysis compared with PCR, where a minimum amount of tumour (comprising at least ∼20% and often 50% of the sample) is typically required.…”