Fig 2: Representative staining results for the mismatch repair (MMR) protein expression and BRAF mutation through immunohistochemistry. (a) Colorectal sections using an antibody towards the MMR protein showing positive nuclear staining (magnification = 400 ×). (b) Colorectal cancer sections using an anti-BRAF V600E antibody, showing positive cytoplasmic staining (magnification = 400 ×).

Fig 3: (a–e) Cutaneous phenotype of the five BRAF-mosaic patients with a multinodular phenotype. (f–i) Cutaneous phenotype of two BRAF-mosaic patients without the multinodular phenotype, both presenting with a medium congenital melanocytic naevus and > 200 smaller naevi [patient 6 (f, g) from Table 2, and patient 7 (h, i) from Table 2].

Fig 4: Sanger sequencing trace of DNA extracted directly from (a) congenital melanocytic naevus (CMN) tissue (upper) and DNA extracted from cultured naevus cells (lower) from the same patient, demonstrating BRAF c.1799T>A, p.(V600E) in both, which appears low-level somatic in whole tissue and heterozygous in naevus cells. (b) A similar phenomenon is observed in naevus cells cultured directly from a patient with NRAS c183A>G, p.(Q61R). Immunocytochemistry of BRAF p.(V600E) naevus cells shows pancytoplasmic uniform expression of BRAF V600E (green) in all naevus cells. Cells are counterstained with Hoechst stain (blue) and Alexa Fluor 647-conjugated phalloidin antibody (red). BRAF V600E negative control at original magnification × 20 (c), and BRAF V600E immunostaining at × 20 (d) and × 63 (e).