Severity Score:

• 0 = Normal,
• 1 = Mild (observation barely perceptible and not believed to have clinical significance),
• 2 = Moderate (observation visible but involves minor proportion of tissue and clinical consequences of observation are most likely subclinical),
• 3 = Marked (observation clearly visible involves a significant proportion of tissue and is likely to have some clinical manifestations generally expected to be minor),
• 4 = Severe (observation clearly visible involves a major proportion of tissue and clinical manifestations are likely associated with significant tissue dysfunction or damage)

Significance Score:

• 0 = Not significant: Interpreted by the histopathologist to be a finding attributable to background strain (e.g. low-incidence hydrocephalus, microphthalmia) or incidental to mutant phenotype (e.g. hair-induced glossitis, focal hyperplasia, mild mononuclear cell infiltrate).
• 1 = Significant: Interpreted by the histopathologist as a finding not attributable to background strain and not incidental to mutant phenotype.