Nonpalpable mammographically occult invasive breast cancers detected by MRI.

Overview

OBJECTIVE: The purpose of this study was to determine the MRI findings and histology of clinically and mammographically occult invasive breast cancers detected by MRI. MATERIALS AND METHODS: A retrospective review was undertaken of 1,336 breast MRI examinations performed during a 2-year period. Among these, 68 nonpalpable mammographically occult invasive cancers were identified in 57 women with a median age of 50 years (range, 30-72 years). MRI findings were classified according to the breast MRI lexicon. Medical records were reviewed to determine the histology. RESULTS: Indications for performing MRI were extent of disease assessment in 72% (41/57), high-risk screening in 25% (14/57), and problem solving in 3% (2/57). MRI lesion types in these 68 invasive cancers were nonmass in 57% (39/68) and mass in 43% (29/68). Kinetics were plateau in 59% (40/68), washout in 38% (26/68), and persistent in 3% (2/68). Histology was invasive ductal cancer in 65% (44/68), mixed invasive ductal and lobular cancer in 19% (13/68), and invasive lobular cancer in 16% (11/68). The cancer stage was I in 61% (34/56), II in 32% (18/56), and more advanced in 7% (4/56). Sixty-three percent (43/68) of lesions were minimal cancers, defined as invasive cancers measuring under 1 cm. CONCLUSION: In this study of mammographically and clinically occult cancers detected by MRI, 57% (39/68) of invasive breast cancers were evident as nonmass enhancement, and 63% were minimal breast cancers.