Retroperitoneal mass with cystic change - DDx paraganglioma, schwannoma, ANNUBP

Neurofibromatosis type 1-associated Nerve Sheath Tumors


Neurofibroma (NF)
Plexiform NF
Neurofibroma with atypia (“ancient neurofibroma”)
Cellular NF
Atypical neurofibromatous neoplasm of uncertain biological potential (ANNUBP)
MPNST, low-grade
MPNST, high-grade



Nomenclature for the NF1-associated Nerve Sheath Tumors

ANNUBP
Schwann cell neoplasm with at least 2 of 4 features
cytologic atypia, loss of neurofibroma architecture, hypercellularity, mitotic index more than 1/50 HPFs and less than 3/10 HPFs



MPNST, low-grade
Features of ANNUBP, mitotic index 3-9/10 HPFs & no necrosis



MPNST, high-grade
≥ 10 mf/10 HPFs or 3–9 mf/10 HPFs combined with necrosis


Neurogenic tumor, e.g. schwannoma, paraganglioma, & ANNUBP may show prominent cystic degeneration
Strong enhancement may not be seen on paraganglioma
Gradual strong enhancement on MRI may be seen on various neurogenic tumors