Level 1
Nuclei absent or inconspicuous under 400× microscopy, basophilic
Grade 2
Nuclei distinct at 400×, eosinophilic, visible but not prominent at 100×
Grade 3
100× nuclei clearly visible, eosinophilic
Grade 4
Significant nuclear pleomorphism, polymorphic giant cells and/or rhabdomyosarcoma-like and/or sarcoma-like differentiation may be seen