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High-Risk Lesions

Lobular Carcinoma In Situ (LCIS)

Despite the word "carcinoma," classic LCIS is not cancer - it is a risk marker that tells you future breast cancer risk is elevated in both breasts.

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Home › Breast Education › Common Findings › LCIS
Quick Take: Despite its name, lobular carcinoma in situ (LCIS) is not cancer in the traditional sense. Classic LCIS is a marker lesion - a finding that tells you the risk of developing breast cancer in the future is elevated. It does not mean cancer is present now, and it does not require cancer treatment. Found in approximately 1–5% of breast biopsies.
⚠ High-risk lesion: High-risk lesions are not cancer, but they can be associated with a higher risk of developing cancer or may require surgical removal in some cases.

Understanding the Name

Lobular
The abnormal cells are in the lobules - the milk-producing glands
Carcinoma
The cells look like cancer cells under the microscope - but they are NOT invading surrounding tissue
In Situ
Confined to where they started - NOT breaking through the lobule walls, NOT spreading

LCIS does not grow into surrounding breast tissue. It does not form a lump. It does not spread to lymph nodes. It is almost never detectable on imaging - it is found incidentally when a biopsy is performed for a different imaging finding.

Classic vs. Pleomorphic LCIS

Classic LCIS

  • Treated as a risk marker, not cancer
  • Annual mammography ± enhanced MRI
  • Chemoprevention discussion
  • Surveillance often preferred over excision (if concordant)
  • Most common form

Pleomorphic LCIS

  • More aggressive cellular features overlapping with high-grade DCIS
  • Higher upgrade rate
  • Surgical excision typically recommended
  • Managed more like DCIS

Is This Cancer?

Classic LCIS is not cancer. It does not invade surrounding tissue or spread to lymph nodes. However:

8–10×

Women with LCIS have approximately 8–10 times the average lifetime risk of developing breast cancer. This elevated risk affects both breasts equally and persists for decades - it is not limited to the breast where LCIS was found.

What Happens Next

Classic LCIS, concordant
Risk counseling + surveillance

Annual mammography with consideration of supplemental MRI. Chemoprevention discussion - tamoxifen can reduce future cancer risk by approximately 50%.

Classic LCIS, discordant or with pleomorphic features
Surgical excision recommended

Excision needed to ensure no adjacent cancer was missed.

Pleomorphic LCIS
Surgical excision recommended at most institutions

Treated more aggressively due to overlapping features with high-grade DCIS.

Excision returns benign
Long-term enhanced surveillance continues

Risk remains elevated - ongoing mammography and possible MRI recommended.

Risk reduction
Tamoxifen or aromatase inhibitors

Chemoprevention reduces future cancer risk by approximately 50%. Discuss this option actively with your doctor.

When Should I Be Concerned?

Take action if:

Related Topics

→ ADH → ALH → Radial Scar → Papilloma → Does It Increase My Risk? → Do I Need Additional Screening?

Does your biopsy report mention LCIS? The most important determination is whether it is classic or pleomorphic, and whether it was concordant with the imaging finding. A board-certified radiologist with subspecialty breast imaging experience can walk you through it step by step.

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This content is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider with any concerns about your breast health.