Sonographic and pathologic findings in typical and atypical medullary carcinomas of the breast

PURPOSE: We investigated whether there was a relationship between the sonographic and histologic appearances of medullary carcinomas of the breast to determine whether sonography is helpful in the differentiation of typical and atypical medullary carcinomas. METHODS: We retrospectively reviewed the histologic slides and sonograms of 20 patients who had been diagnosed with medullary carcinoma of the breast. We then classified the carcinomas as typical or atypical based on strict histologic criteria. We also evaluated the relationship between sonographic findings and the histologic reclassification. RESULTS: Eight (40%) of the 20 medullary carcinomas were classified as typical, and 12 (60%) were classified as atypical. On sonography, a smooth outline was visualized in 6 (75%) of the 8 typical medullary carcinomas but in none of the 12 atypical carcinomas. A jagged margin was sonographically visualized in 10 (83%) of the 12 atypical carcinomas, and a focal irregularity in the margin was visualized in 2 (17%) of the 12 atypical carcinomas. Four of the typical medullary carcinomas had posterior enhancement, and 9 of the atypical medullary carcinomas showed retrotumoral shadowing. The difference in tumor-margin regularity between typical and atypical medullary carcinomas was found to be statistically significant (p < 0.001) using the 2-tailed Fisher's exact test. CONCLUSIONS: To prevent overdiagnosis of medullary carcinoma, a thorough pathologic review of the entire tumor is recommended if sonography shows a jagged margin or a margin with focal irregularity.