Objective: N-methyl-N-nitrosourea (MNU) is a chemical carcinogen frequently used to induce mammary tumors in female rats, which experimental evaluation requires the monitoring of tumor's volume. For this purpose several methods are described, namely: caliper and ultrasonography measurement. The aim of this work was to compare data obtained by caliper and ultrasonography. Method: Twelve female Sprague-Dawley rats with 187.7± 14.3 g body weight were intraperitoneally injected with MNU (50 mg/Kg) at 50 days of age. Thirty-six weeks after MNU administration forty-one tumors volume was determined by caliper (Vito®) and ultrasonography (LOGIQP6®, General Electric Healthcare) measurement. The tumor volume (V) was calculated according to the following formula V=π.〖S_1^2〗^.S_2⁄12, being S_(1) and S_2 the tumor diameters (S_(1)<S_(2)). Results: The means tumor caliper and ultrasonography measures were 4.116±5.801 cm3 and 2.578±4.302 cm3, respectively. The ICC for scoring reproducibility was 0.75 (95 % Confidence Interval, 0.57 to 0.86) and Paired-Sample T-Test was significant (p<0.01). Conclusion: Usually mammary tumors in rat are measured by caliper. However, our results showed that there are volume differences between both methods studied. Ultrasonographic method is more accurate and more precise than caliper. Therefore, we recommend the use of ultrasonography to rat tumor evaluation. Objective: There is a significant percentage of patients with breast cancer and HER2 receptor overexpression that do not respond to trastuzumab-directed therapy. The aim of this paper is to study the alterations of one of the HER2 signalling pathways related to trastuzumab response in breast cancer. Method: The study comprised 127 cases of breast carcinoma in different stages of evolution with HER2 overexpression (HercepTest 3+) or gene amplification (FISH). All patients were treated with trastuzumab. The assessment of PTEN and pAkt expression was based on staining intensity and percentage of stained cells. We also determined the molecular alterations in PIK3CA. Results: Our series showed a statistically significant association between a positive expression of PTEN and the absence of PIK3CA mutations with better overall survival from treatment onset with trastuzumab (p=0.022 and p= 0.003, respectively). The association with the expression of pAkt was statistically significant if survival is evaluated from the pathological diagnosis of the tumor (p=0.043), pAkt positive tumors had worse survival. Objective: Expression of mammaglobin A (MG-A) in breast cancer has been reported to be of prognostic value and to be associated to hormone receptor-positivity. MG-A is also useful in the diagnosis of metastatic breast cancer. The present study evaluates the differential MG-A expression in two subsets of primary breast cancer (metastasizing vs. non-metastasizing) and in their correspondent metastases. Method: Immunohistochemical analysis of MG-A (clone 304-1A5) was performed in 55 non-metastasizing primary breast tumors and 19 paired primary and metastatic breast cancers. A percentage of 1 % of stained tumor cells was considered positive. The expression of MG-A in the different groups, together with other clinicopathologic factors (grade, size, hormone receptors, HER2, etc.) was analyzed by t-test. Results: Expression of MG-A was significantly higher in estrogen receptor-positive (ER+) tumors (p<0.003). A trend was noted for ER + metastasizing primary breast cancers to show a higher expression of MG-A, compared to those nonmetastasizing (p=0.064). No significant differences were noted in the expression of MG-A between metastasizing primary tumors and their correspondent metastases, with a good correlation (p=0.033). Conclusion: These results suggest that MG-A might be of prognostic value in determining a subset of ER + breast cancers prone to progression. Larger series are needed to confirm these observations.