Neurosurgery notes/Tumours/Cranial and paraspinal nerve tumours/Neurofibroma/Atypical neurofibromatous neoplasm of unknown biological potential (ANNUBP)

Atypical neurofibromatous neoplasm of unknown biological potential (ANNUBP)

View Details
Status
Done
logo
Parent item
Neurofibroma

General

  • Is an NF1-associated tumor with worrisome features of malignant transformation that is still quantitatively insufficient for a definitive diagnosis of Malignant peripheral nerve sheath tumor (MPNST)
  • CANNOT BE USED FOR SPORADIC NON NF1 LESIONS
  • AKA Atypical Neurofibromas

Definition

  • In the setting of NF1:
    • Schwann cell neoplasm with at least two of the following four features:
      • Cytological atypia
      • Loss of neurofibroma architecture
      • Hypercellularity
      • A mitotic count of > 0.2 mitoses/mm2 and < 1.5 mitoses/mm2 (> 1 mitosis/50 HPF and < 3 mitoses/10 HPF')

Genetics

  • Strongly associated with
    • Deletions of the CDKN2A and/or CDKN2B locus encoding cell cycle regulators
      • p16 (p16INK4a) encoded by CDKN2A
      • p14ARF (encoded by CDKN2A)
      • p15 (p15INK4b; encoded by CDKN2B)
  • Does not yet contain
    • Presence of SUZ12 or FED mutations, leading to H3 p.K28me3 (K27me3) loss
      • This is restricted to MPNST

Pathology

  • Micro
      • Tumours designated as ANNUBP in patients with neurofibromatosis type 1 may have several worrisome features, including cytological atypia.
      Tumours designated as ANNUBP in patients with neurofibromatosis type 1 may have several worrisome features, including cytological atypia.
      ANNUBP with increased cellularity and mitotic activity, but otherwise falling short of a malignant diagnosis.
      ANNUBP with increased cellularity and mitotic activity, but otherwise falling short of a malignant diagnosis.