RESUMEN
PURPOSE: Elastography was primarily used as an adjunctive method along with ultrasonography in differentiation between benign from malignant lesions. Occasionally, overlaps can occur which are caused by some rare invasive breast cancers. Our aim is to analyze the role of rare breast cancers in false negative strain elastography results and to assess the relation among false negative results and tumor size, lesion distance to skin, and tumor grade. METHODS: Patients with BI-RADS 5 category underwent strain elastography and core biopsy. All those with confirmed invasive breast cancer were included. For each rare breast cancer, four usual invasive breast cancer cases were taken as a control group. The cut-off value of strain ratio was considered as 2.3. The true positive and the false negative groups were compared in terms of histological type (rare carcinomas and the others) and the other parameters. Pearson Chi-square and Fisher's exact test were used for statistical analyses. P values < 0.05 were considered statistically significant. RESULTS: One hundred-thirteen patients were defined as true positive (70.6%), and 47 patients were defined as false negative (29.4%). Strain ratio values of the rare breast cancers were significantly lower than those of the other breast cancers (p = 0.012). There was no statistically significant difference between the groups with respect to tumor size, distance to skin, and tumor grade (p > 0.05). CONCLUSION: The rare breast cancers are an important cause of false negativity in elastographic evaluation of invasive breast cancers. The results should be interpreted in combination with grayscale US findings.