Characteristic/ degree of atypia Absent Mild Moderate Severe Nucleus size <kn  ≥ kn 1- 2x ≥ kn >2x kn Nucleus shape Ovoid or fusiform Ovoid and/or fusiform and/or irregular Ovoid and fusiform or irregular Irregular Nuclear variability Minimal Minimal or moderate Moderate Severe Nucleus chromatin Homogeneous Homogeneous or hyperchromatic Hyperchromatic (irregular nuclear membrane) Hyperchromatic (irregular nuclear membrane) Nucleolus Not evident (absent) Not evident (absent) or evident (but not prominent-small) Not evident (absent) or evident (but not prominent-small) Evident-Prominent (large) Cytoplasm amount Scarce Usually scarce, but sometimes abundant or variable Usually scarce, but sometimes abundant or variable Abundant KN=Keratinocytes; Distribution: Mild atypia- 0-5% of cells; Moderate atypia- 6-10% of cells; Severe atypia- >10% of cells

Table 1: Definitions of nuclear atypia for GMN adapted from Weinstock et al. [12], Culpepper et al.[13], and Braun-Falco M et al. [14].