A 30-year-old woman was 24 weeks pregnant and noted a left breast lump. (A) Radial and (B) antiradial ultrasonographic images show a circumscribed oval mass isoechoic to fat with internal echogenic septations (arrowheads). Biopsy showed lactating adenoma. (Courtesy of Dr Ellen Mendelson, Feinberg School of Medicine, Northwestern University, Chicago, IL, via SuperSonic Imagine.)