ILC explained

Understanding invasive lobular carcinoma

Sources checked: September 2026

The short version

ILC (invasive lobular carcinoma) starts in the lobules — the milk-producing glands — rather than the ducts, and can grow in a pattern that is sometimes harder to feel as a distinct lump or see clearly on a mammogram.

(invasive lobular carcinoma) is the second most common type of invasive breast cancer, after . It starts in the lobules — the glands that produce milk — rather than in the milk ducts.

Why it can look different on imaging

ILC sometimes grows in a single-file pattern through breast tissue rather than forming one solid lump, which can make it less noticeable on a mammogram or exam than other types. A breast MRI is sometimes used alongside a mammogram to get a fuller picture.

ILC is often ER-positive. Many of the same staging, grading, and biomarker principles that apply to other invasive breast cancers apply here too — ask your care team how they specifically apply to your case.

Questions you may want to ask

  • Did imaging capture the full extent of the disease, or is more imaging recommended?

  • How does ILC affect the surgical approach you are recommending?

RelatedDCIS and IDC: what the terms mean

Sources