Morphometric analysis of AgNORs in tubular and papillary parts of canine mammary gland tumors.

Objective: To test the value of the silver staining nucleolar organizer regions (AgNORs) technique on canine mammary gland tumors using image analysis and to estimate differences in AgNOR parameters in structurally different parts of canine mammary gland tumors.

Study Design: Analysis was performed on 13 complex type and 10 simple type malignant canine mammary gland tumors containing tubular and/or papillary structures. Ten normal mammary glands were used as controls. Morphometric analysis was done by a computer-assisted image analysis system and consisted of evaluation of nuclear area, number and area of AgNORs per nuclear area, ratio of nuclei with five or more AgNORs, nuclear perimeter, area fraction between nuclear area and area of AgNORs, and area, equivalent diameter, volume equivalent sphere, perimeter and circularity of a singular AgNOR.

Results: Distinct differences were detected between normal and malignant mammary gland tissue for all measured parameters. There were no significant differences between the tubular and papillary parts of the same tumor or between the tubular and papillary parts of complex and simple type tumors.

Conclusion: Despite the fact that no significant differences were found for AgNOR parameters between papillary and tubular structures of mammary gland tumors, the results of grouping tumors by the number of AgNORs indicate that this might help with classification of canine mammary gland tumors.