Figure 2
Spitzoid neoplasm with the BAIAP2L1–BRAF fusion transcript. Analysis of a tumor sample from a 4-year-old African-American female (patient 2) with a 7.8-mm-thick spitzoid melanocytic proliferation on her thigh, sentinel lymph node metastasis at diagnosis, and no evidence of disease at 53 months of follow-up. (a) H&E photomicrograph (4 ×) showing a dome-shaped proliferation of vertically oriented fascicles of spindled melanocytes throughout the reticular dermis. (b) TERT mRNA ISH shows no detectable intracellular signals beyond the background expression in this wild-type TERT promoter melanocytic tumor. (c) Break-apart FISH shows the rearrangement of BRAF with loss of the 5′ end (red signal), consistent with a complex translocation. (d) Break-apart FISH for BAIAP2L1 shows splits of the red and green signals. (e) Schematic representation of the BAIAP2L1–BRAF fusion, showing that the fusion occurred by tandem duplication at 7q21.3-7q34. (f) The fusion transcript is formed by joining exon 12 of BAIAP2L1 (NM_018842, chr7:97933507) to exon 9 of BRAF (NM_004333, chr7:140487384). (g) The fusion product is an 860-amino-acid chimeric protein containing the entire kinase domain of BRAF. (h) The RNA transcript contig shows the fusion breakpoint in the chimeric BAIAP2L1-BRAF transcript.
