NF1 and plexiform neurofibroma: The term “atypical neurofibromatous neoplasm with uncertain biologic potential (ANNUBP)” has been recently coined [6] for a subset of NF1-associated neurofibromatous tumors that exhibit at least two of the following features: (i) nuclear atypia; (ii) hypercellularity; (iii) increased mitotic activity (>1 mitosis/50 HPF but <3 mitoses/10 HPF); and (iv) a variable loss of neurofibroma architecture (i.e., the presence of herringbone and/or fascicular storiform growth patterns) (Figure 9) (Table 6).