What is the differential diagnosis for an intracystic nodule in the breast?
Differential includes both benign aetiologies including papillary apocrine metaplasia (PAM - most common), tumefactive sludge or layering lipid - as well as the spectrum of papillary lesions from papilloma to papillary carcinoma.
What morphologic features help identify suspicious intracystic mural nodules?
Loss of thin echogenic outer cyst wall along points of attachment; extension beyond the cyst into ducts; angular margins at point of attachment; internal vascularity.
Complex cystic lesion in the left breast at 2 o'clock 6cm from the nipple, corresponding to the mammographic abnormality. The intracystic solid nodule demonstrates loss of the cyst wall along the points of attachment, angular margins with the cyst wall, probable duct extension (see the first image) and internal vascularity - all of which are suspicious features for malignancy.