NF1 and plexiform neurofibroma: Detection of the causal NF1 PVs in individuals with a mosaic/segmental phenotype requires special attention to (1) the sensitivity of the technology used to detect variants, as well as (2) the type of cells to be analyzed in affected tissue if the variant is not detectable in blood, i.e., melanocytes (but not keratinocytes or fibroblasts) from CALMs37 or Schwann cells from the cutaneous or plexiform neurofibromas.40