Role of sonography in diagnosing and staging invasive lobular carcinoma.

Purpose: The goal of this study was to compare the sensitivity of sonography with that of mammography in the detection of invasive lobular carcinoma (ILC), to identify ILC's typical imaging characteristics, and to further show the important role of ultrasound in the staging and treatment planning of this elusive tumor.

Methods: We identified all patients with ILC seen at our institution from 1998 through 2001; 62 had pathologically proven pure ILC. We retrospectively reviewed and analyzed the sonographic appearances in correlation with mammographic, pathologic, and clinical findings. We reviewed the results of sonographic examinations of the nodal basins and fine-needle aspiration (FNA) of suspicious nodes and correlated them with initial clinical and final pathologic staging. We noted all cases of multicentricity or multifocality and analyzed the relative sensitivity of mammography and sonography according to tumor size.

Results: Sonography had a sensitivity of 98% versus 65% for mammography. The most common mammographic pattern was a spiculated mass or architectural distortion (39%). On sonography the most common pattern was a hypoechoic mass with (58%) or without (27%) shadowing. An infiltrative pattern was observed in 13% of the cases. Ultrasound-guided FNA confirmed disease was present in the axillary lymph nodes in 21% of the patients, and sonographic examination of the nodal basins resulted in a change of clinical staging from N0 to N1 in 75% and from N1 to N0 in 30% of the cases. Multicentricity/multifocality was identified sonographically and proved by FNA in 21% of patients.

Conclusions: Sonography has a much higher sensitivity than mammography in detecting ILC and therefore is an important adjunctive tool in the diagnosis of this form of cancer. Routine examination of node-bearing areas in patients with ILC proved useful in refining the disease staging.