Diagnostic imaging of lobular carcinoma of the breast: mammographic, ultrasonographic and MR findings

PURPOSE: To evaluate the most frequent mammographic, US and MR findings of invasive lobular carcinoma and the role of MRI in defining multifocality and/or multicentricity of this tumor histotype. MATERIAL AND METHODS: We studied 45 lobular carcinomas (39 patients) were selected from 421 breast cancers. Core biopsy with a 14 G needle was performed in 39 cases, under US guidance in 36/39 and under mammographic guidance in 3/39 cases. Surgical biopsy was performed in 2 cases and the diagnosis could be made only after mastectomy in 5 cases. All patients were examined with mammography and US and (10-13 MHz) and 8 also with MRI. RESULTS: 28/46 palpable lesions (60.9%). Core biopsy correctly diagnosed 38/39 lesions (97.4%). The most frequent mammographic findings was that of a nodular opacity without microcalcifications (34.8%), followed by a mass with spiculated borders (30.4%). Microcalcifications were seen in one case only (2.2%). Mammography detected no abnormalities in 15.2% of cases, but US showed a lesion in 2 of these cases. The most frequent US pattern was that of a hypoechoic lesion (43.5%), followed by posterior US beam attenuation. No US signs of abnormality were seen 15.2%. MRI correctly detected 13 lesions. Contrast enhancement was greater than 70% at one minute in 10 cases and greater than 40% in one case; two lesions exhibited atypical slow contrast enhancement, peaking at 5 minutes. MRI detected 5 lesions missed at both mammography and US and showed multifocal (3 and 2) lesions where the other techniques had detected one lesion only. DISCUSSION: At mammography and US invasive lobular carcinoma exhibits no different features than ductal carcinoma but is difficult to identify especially in its early stages. US is a useful tool especially to characterize mammography-detected lesions but in our experience it also demonstrated 2 lesions missed at mammography. MRI is a precious examination to define the multifocal, multicentric or bilateral character of invasive lobular carcinoma. CONCLUSIONS: Invasive lobular carcinoma of the breast is often very difficult to diagnose. Thus, we suggest the use of integrated diagnostic imaging with mammography, US and, in some cases, MRI for earlier diagnosis and to identify further tumor localizations.