OBJECTIVE: This study aims to investigate the association between the immunohistochemical expression of matrix metalloproteinase-2 and matrix metalloproteinase-9 and plasma zinc in women with fibroadenoma. METHODS:This cross-sectional study included 37 premenopausal women with fibroadenoma. Waist circumference and body mass index of the participants were measured. Plasma zinc concentrations were determined using atomic flame absorption spectrophotometry. Fragments of breast tissue were fixed and incubated with primary mouse monoclonal antibodies (monoclonal antibodies matrix metalloproteinase -2 -507 and monoclonal antibodies matrix metalloproteinase -9-439). Semi-quantitative analysis of matrix metalloproteinase-2 and matrix metalloproteinase-9 immunoreactivity was performed. Spearman's test and Friedman's test were used for statistical analyses. The p<0.05 were considered statistically significant. RESULTS:The average age of the participants was 32.81±9.51 years. The body mass index and waist circumference values were within the normal range. The mean plasma zinc concentration was 42.73±13.84 μg/dL, with 94.6% inadequacy. A statistically significant difference was found between the positive expression of matrix metalloproteinase-2 and matrix metalloproteinase-9 (p=0.0184). There was no significant correlation between the matrix metalloproteinase expression and the plasma zinc levels.CONCLUSIONS: Women with fibroadenoma had hypozincemia and positive expression of metalloproteinases.