Magnetic resonance mammography (MRM) of a 53-year-old patient during hormone replacement therapy (HRT) with a small histologically proven invasive lobular cancer in the left breast. (a) The subtraction image 420 s after contrast medium (CM) administration showed a bilateral, almost symmetrical, enhancement. (b) The time–intensity curve of the right breast indicated a continuous rise of the signal intensity of 41% (curve type II). Additionally, a round blurred area of stronger CM enhancement was detectable just behind the nipple of the left breast. The lesion was not obscured by hormone-associated CM enhancement and showed a rapid CM enhancement followed by a plateau phenomenon, which is characteristic for curve type IV suggesting suspicion of malignancy. Eight months after breast-conserving therapy, a MRM for follow-up was performed without hormonal medication. (c) The subtraction images showed a weaker bilateral enhancement. (d) The time–intensity curve indicated a weak increase of signal intensity less than 25%, reflecting a decrease by one curve type after withdrawal of HRT. R, right; L, left.