Pure lobular carcinoma of the breast presenting as a hyperechoic mass: incidence and imaging characteristics.

OBJECTIVE: The purpose of this study was to determine the proportion of invasive lobular carcinomas with increased sonographic echogenicity.

MATERIALS AND METHODS: A retrospective review of mammographic and sonographic findings included cases of pure invasive lobular carcinoma with available images from January 1998 to June 2010. We assessed ultrasound images for the presence of a mass, internal echogenicity, margin characteristics, and attenuation effects. In hyperechoic tumors, more than 90% of the mass had increased echogenicity compared with surrounding fat. In heterogeneously echogenic tumors, the echogenic component constituted 20-90% of the tumor. Findings at mammography, MRI, and surgery were correlated with sonographic findings. A breast pathologist reviewed histologic findings and confirmed the diagnosis of pure invasive lobular carcinoma.

RESULTS: Of 509 invasive lobular carcinomas, 27 (5%) were hyperechoic, of which 13 (48%) were associated with posterior acoustic shadowing. Heterogeneously echogenic cancer was seen in 57 (11%) cases. The most common sonographic finding was a hypoechoic, irregular mass with or without posterior shadowing (n = 323; 63%). In 66 (13%) lesions, focal shadowing was seen without a discrete mass. Fourteen (3%) lesions were isoechoic with respect to surrounding normal adipose tissue without acoustic shadowing. Twenty-two (4%) of the malignant tumors were not identified sonographically. Of these, 15 (68%) had mammographic abnormalities, one (5%) was seen at MRI, and six (27%) presented as palpable masses that were surgically excised.

CONCLUSION: Pure invasive lobular carcinomas can present as a hyperechoic mass or with substantial hyperechoic component. All sonographic lesion characteristics should be evaluated and biopsy recommended when there are suspicious features, even in a lesion that is predominantly hyperechoic.