Table 5

Recommendations for mouse work-up for PNSTsa

Grade I lesions: perform S-100:
 Diffuse positivity → GEM schwannoma
 Focal positivity → GEM neurofibroma
 Negative → EM is essential.
 With Schwann cell or perineurial differentiation on EM → GEM neurofibroma
 No Schwann cell or/and perineurial cell differentiation on EM → tumor is not a GEM PNST and should be classified according to EM features or markers as fibrosarcoma, rhabdomyosarcoma, spindled cell carcinoma, etc.
Grade II or III lesions: perform S-100, desmin, actin:
 Diffuse S-100 positivity → GEM schwannoma
 With other markers positive → GEM schwannoma grade II or III with divergent differentiation (Triton tumor)
 With focal S-100 positivity → GEM PNST grade II or III
 With other markers positive → GEM PNST grade II or III with divergent differentiation.
 Negative for S-100 → EM (essential).
 With Schwann cell or perineurial differentiation on EM → GEM PNST grade II or III
 Without Schwann cell or perineurial differentiation on EM → not a GEM PNST and should be classified according to EM features or markers as fibrosarcoma, rhabdomyosarcoma, spindled cell carcinoma, etc.
  • a PNST, peripheral nerve sheath tumor; EM, electron microscopy.