Neurofibroma diagnostic criteria

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sara Mohsin, M.D.[2]

Overview

Following is the general diagnostic criteria for neurofibroma:

Randomly oriented thin spindled cells with wavy, hyperchromatic nuclei
- Cellularity and organization are generally insufficient to produce palisading
- Thin processes with indistinct cytoplasm
- Most nuclei are small and bland
Generally hypocellular
- Thin and thick collagen strands (“shredded carrot collagen”)
- Variable myxoid material surrounding cells and collagen
- Occasional mast cells and lymphocytes, rare foam cells
Diffusely S100 immunoreactive
Entrapped axons of overrun nerve frequently scattered within lesion
- Nerve frequently not grossly identifiable
May show localized hyperchromatic atypical cells (“ancient change”)
- Localized cells with large, pleomorphic nuclei, cytoplasmic intranuclear inclusions, smudgy chromatin, and inconspicuous nucleoli
- Often large, long standing lesions
- Low mitotic index