Your pathology report for fibroepithelial lesion of the breast

By Jason Wasserman MD PhD FRCPC
October 3, 2025

A fibroepithelial lesion is a term pathologists use to describe a group of breast tumors that contain both epithelial cells (cells that line breast ducts) and stromal cells (the connective tissue that supports the ducts).

This is not a final diagnosis. Instead, it is used when the tissue sample from a biopsy is too small to determine whether the lesion is a fibroadenoma (a common, benign tumor) or a phyllodes tumor (a rare tumor that can be benign, borderline, or malignant).

Why is this diagnosis made?

When only part of a tumor is sampled, as in a core needle biopsy, the pathologist may not see enough of the overall growth pattern to decide between fibroadenoma and phyllodes tumor. Because the two tumors can look very similar under the microscope, the safest and most accurate way to describe the finding is to call it a fibroepithelial lesion.

Fibroadenoma vs phyllodes tumor

Fibroadenomas and phyllodes tumors are both fibroepithelial lesions, but they differ in behavior and management.

Feature Fibroadenoma Phyllodes tumor
Frequency: Very common, especially in young women Rare
Behavior: Benign (noncancerous) Can be benign, borderline, or malignant
Growth: Usually slow-growing, stable in size May grow quickly and become large
Risk of recurrence after removal: Low Higher, especially if margins are positive
Chance of spreading: Does not spread Malignant phyllodes tumors can spread to other parts of the body (rare)
Treatment: May be monitored or removed Usually removed with a margin of normal tissue to reduce risk of recurrence

What happens next?

If a fibroepithelial lesion is reported, doctors often recommend either:

  • Surgical removal of the lump, so the entire tumor can be examined under the microscope.

  • Close follow-up with imaging, depending on the size and features of the lump and the patient’s clinical situation.

Once the entire lesion is removed, the pathologist can usually make a definite diagnosis.

Questions to ask your doctor

  • Does my biopsy show a fibroepithelial lesion?

  • Do you think this is more likely a fibroadenoma or a phyllodes tumor?

  • Do I need surgery to remove it, or can it be monitored?

  • If surgery is needed, what does it involve?

  • What will the next steps be once a final diagnosis is made?

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