MIB-1 labelling indices according to clinico-pathological variables in canine mammary tumours: a multivariate study

The relationship between MIB-1 labelling indices (LI), as detected by immunohistochemical methods, and other clinico-pathological characteristics was studied in a series of 77 malignant mammary tumours surgically removed from 47 female dogs. The immunostaining was assessed on the basis of the estimated percentage of positive cells in the areas of highest labelling. Multivariate logistic regression demonstrated no influence of breed, age, previous pregnancies, previous progestin administration, histological type or location of the tumour on MIB-1 LI. MIB-1 LI was significantly related to the size of the tumour, necrosis, invasive growth and histological grade, but not with ulceration, lymph node metastasis, skin fixation or E-cadherin expression. The significant relationship between MIB-1 LI and other known factors of poor prognosis suggests that a high LI may have prognostic value in canine malignant mammary tumours.