We report two cases of invasive lobular carcinoma of the breast that were initially missed on first mammographic interpretation because of an uncommon, easily overlooked, and unreported imaging presentation. The abnormality in the cases manifested as an apparent decrease in breast glandular tissue volume when compared with the patients' previous mammograms, observed as "shrinking" of the breast on mammography. Invasive lobular carcinoma is considered one of the most difficult subtypes of breast cancer to identify on mammography because the changes that occur are often nonspecific and subtle. Microcalcifications that are usually associated with breast masses on imaging are rarely seen in this subtype of breast cancer. Although magnetic resonance imaging and computer-aided detection have somewhat improved the detection of invasive lobular carcinoma, radiologic and clinical detection remains a challenge.