This young man with NF-1 mutation developed a slow growing mass on his thigh. The mass was ill-defined and measured several centimeters in greatest dimension. There was a reported "bag of worms" quality to the mass, as is often the case with plexiform neurofibromas. This gross description is due to the tumor snaking around as a tube in three dimensions. When this is cut on a two dimensional slide, it appears as separate circumscribed nodules, as in this case. The tumo is made up of multiple cell types, the cells normally observed in the nerve sheath - mast cells, fibroblasts, Schwann cells, etc. The plexiform variant is virtually pathognomonic neurofibromatosis type 1.
The tumor is made up of mulltiple cell types, including fiboblasts, Schwann cells and interspersed mast cells. These appear well-contained within the nerve sheath. Thre is no significant cytologic atypia or mitotic activity. The stroma is fibromyxoid.