Ultrasonographic evaluation of invasive lobular carcinoma.

PURPOSE: To compare ultrasonographic (US) and mammographic findings and tumor size measurements of invasive lobular carcinoma (ILC). MATERIAL AND METHODS: US diagnoses and mammographic findings were compared in 95 patients with pure ILC, including 46 palpable and 49 nonpalpable tumors. The diameters of tumors measured by mammography, US, and pathology were compared in 70 of the 95 patients using scatter plots and correlation analysis. RESULTS: Eighty-two (86.3%) of the ILCs were correctly diagnosed as malignant tumor, 5 (5.3%) were diagnosed as focal abnormality, and only 2 patients had normal findings on US. The most common mammographic findings were a spiculated mass (57%) and a focal asymmetric density (15%). US correctly diagnosed 8 of 12 patients with normal or equivocal mammographic findings. The correlation of tumor size assessment on imaging and pathology revealed that US measurements including the "halo" (r=0.69) was superior to that of mammography (r=0.59). ILCs larger than 30 mm were heavily underestimated by both methods. CONCLUSION: Malignant tumor was diagnosed on US in most of the patients with ILC. US tumor measurement including the "halo" predicted tumor size most accurately. The correlation between imaging measurements and tumor diameter on histology was lower for ILCs than reported for populations of mixed carcinomas.