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Table 2 Scoring description for histopathological examination of the sections.

From: Immunohistochemical detection of piscine reovirus (PRV) in hearts of Atlantic salmon coincide with the course of heart and skeletal muscle inflammation (HSMI)

Pathological description - epicard Pathological description - myocard
Score 0: No pathological changes observed. Score 0: No pathological changes observed.
Score 0.1-0.9: Focal/multifocal (2-4 foci) of inflammatory cells lifting the epicardial layer from the surface of the heart, typically 2-3 cell layers thick. Limited number (countable) of mononuclear inflammatory cells infiltrating the epicardium. Score 0.1-0.9. Vascular changes in the small vessels of the compact layer characterized by enlarged endothelial cells, typically stretching out. Minor inflammatory changes of the compact layer without significant involvement of the spongious layer.
If there is only involvement of epicard with minor or very little compact layer involvement; max 1.5 score (diffuse and >5 cell layer thick for most of the inflamed area).  
Score 1-1.9: Diffuse infiltration of inflammatory cells (mononuclear) >5 cell layers thick in most of the epicard present. The infiltration of cells is multifocal to diffuse and can involve parts of or the entire epicardium available for assessment. Score 1-1.9: Focal to multifocal inflammatory foci (2-5 foci) of the compact layer and/or in the spongious part (2-5 foci). Extension typically seen along small vessels and perivascular infiltration.
Score 2.0-2.9: Diffuse infiltration of inflammatory cells (mononuclear) >10 cell layers thick in most of the epicard present. Moderate pathological changes consisting of high number (uncountable) of inflammatory cells in the epicardium. Score 2.0-2.9: The changes in the compact layer are multifocal or diffuse in areas and typically concentrate along small blood vessels. Combined with multifocal to diffuse changes in the spongious layer.
Score 3: Diffusely thickened (>15 cell layers) epicard in more than ¾ of the layer present. Severe pathological changes characterized by intense infiltration of inflammatory cells in the epicardium. Score 3: Widespread to diffuse infiltration of inflammatory cells in the compact layer and involving the spongious layer in a multifocal pattern.
Degeneration and or necrosis of muscle fibers may be/are seen. Atrium can also be involved with inflammatory changes
  1. The sections were scored by histological examination evaluating epicardial and myocardial changes separately. The changes observed were indicated on a visual analog scale (0 to 3) based on the criteria described in the Table.