COL1A1 and plexiform neurofibroma: Looking at the expression level of COL1A1, COL1A2, COL6A1, COL6A2, COL6A3, the results indicate that a sub population of neurofibroma fibroblasts express both collagen type I and VI whereas a low fraction of the neurofibroma fibroblasts sub-population solely express collagen type I or collagen type VI (Fig. 5d, Additional file 1: Figure S3).