Figure 1. Representative Laser microdissection of a primary melanoma demonstrating intratumor heterogeneity of BRAF mutations.
(A) Hematoxylin and Eosin stained primary melanoma with 5 areas to be microdissected marked by squares; (B–F) Higher magnification of microdissected areas demonstrating removal of tumor cells; (G–K) Sequencing electropherograms of the region of BRAF exon 15 in which the T1799A mutation is found. Each sequence is derived from the microdissected tumor region immediately above it. Note the predominant green peak of the mutant allele (A) in panels G & H, but the absence of the mutant allele in panels I, J and K; (L–P) Electropheogram peaks from the BRAF SNaPshot analysis corresponding to the same microdissected tumor areas as the sequencing electropherograms directly above. Note the prominent green mutant peaks in panels L & M, and the smaller but detectable mutant peaks in panels N, O and P. SNaPshot peak heights were used to estimate percentages of mutant alleles in each microdissected sample. In this example the mutant percentages were L = 81%, M = 78%, N = 5%, O = 19% and P = 14%. See Methods for additional details.