Paget Disease of the Breast: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC and Zuzanna Gorski MD
July 2, 2026

Paget disease of the breast (also written Paget’s disease) is a non-invasive type of breast cancer that involves the nipple and the surrounding skin. It is considered non-invasive because the cancer cells are confined to the skin’s surface layer, the epidermis, and have not invaded deeper tissues. Most cases begin in the milk ducts that run from the nipple to the glands deep in the breast, where the abnormal cells first grow as ductal carcinoma in situ (DCIS), another non-invasive breast cancer. Over time, these cells travel up the duct and spread into the nipple and surrounding skin.

The most important thing to understand about Paget disease is that it is usually a sign of another cancer deeper in the breast. Most patients found to have Paget disease of the nipple also have DCIS or an invasive breast cancer in the underlying breast tissue. For this reason, the diagnosis prompts a careful evaluation of the whole breast. This article will help you understand the findings in your pathology report, what each term means, and why it matters for your care.

What causes Paget disease of the breast?

Paget disease of the breast shares risk factors with other, more common types of breast cancer, and in most cases it develops because a cancer already present in the ducts of the breast has spread up into the nipple. Known risk factors for breast cancer include female sex, increasing age, starting menstruation at an early age, and inherited gene changes such as those in BRCA1 or BRCA2. As with other breast cancers, most cases occur in people with no identifiable inherited cause.

What are the symptoms of Paget disease of the breast?

The most common symptom of Paget disease of the breast is a red, scaly, or crusted rash on the nipple and the surrounding skin. These changes often resemble eczema, which can delay diagnosis because the rash may initially be treated as a skin condition. Other symptoms include itching or burning of the nipple, bloody or yellow discharge from the nipple, flattening or pulling inward (retraction) of the nipple, and, in some cases, a lump felt within the breast. Because skin changes can resemble a harmless rash, any persistent nipple change that does not heal should be evaluated.

How is the diagnosis made?

The diagnosis of Paget disease of the breast can only be made after a sample of the nipple skin is examined under the microscope by a pathologist. The tissue is usually obtained by a small skin biopsy of the nipple, such as a punch or wedge biopsy. Under the microscope, Paget disease consists of large, abnormal-looking tumor cells known as Paget cells. These cells are scattered as single cells or small groups within the epidermis, a pattern described as intraepidermal. The Paget cells usually contain a large amount of pale pink cytoplasm, and their nuclei are typically enlarged and pleomorphic (varying in size and shape). A substance called mucin is often found inside certain cells.

Because Paget cells can resemble other conditions of the nipple skin, the pathologist usually performs an immunohistochemical (IHC) test to confirm the diagnosis. Paget cells are typically positive for low-molecular-weight keratins, including cytokeratin 7 (CK7) and CAM5.2. These markers help distinguish Paget disease from two conditions that can appear similar: melanoma (a skin cancer that is positive for markers such as S100, SOX10, and Melan-A) and squamous cell carcinoma in situ (which is positive for p63 and CK5/6). After Paget disease is confirmed, imaging of the breast, usually a mammogram and often an MRI, is performed to look for an underlying cancer and to plan treatment.

Is there cancer in the breast under the nipple?

In most patients, Paget disease of the breast is accompanied by another cancer in the underlying breast tissue. The underlying cancer is most often ductal carcinoma in situ (DCIS) or an invasive ductal carcinoma. For this reason, finding Paget disease on a nipple biopsy usually leads to a full assessment of the breast, and the underlying cancer, when present, drives the stage, prognosis, and treatment plan. In a small number of patients, no underlying cancer is found. These rare cases are thought to arise from specialized cells in the nipple called Toker cells rather than from an underlying duct cancer, and they generally have an excellent outlook.

What does microinvasion mean?

In Paget disease of the breast, microinvasion means that a small number of tumor cells have spread from the epidermis into the dermis, the layer of skin just beneath the surface, in an area measuring 1 mm or less. Microinvasion by itself is not associated with a worse outcome and does not alter the fact that Paget disease is a non-invasive process. What matters most for prognosis is whether a larger invasive cancer is present in the underlying breast.

Biomarker and molecular testing

Biomarker testing is an important part of the workup for Paget disease of the breast, because the results guide treatment for the underlying cancer. The Paget cells, and any underlying DCIS or invasive carcinoma, are tested for the same core breast biomarkers: the estrogen receptor, the progesterone receptor, and HER2.

HER2 — Most cases of Paget disease overexpress HER2, meaning the cells make far more HER2 protein than normal. A HER2-positive result may indicate that HER2-targeted therapies, such as trastuzumab, are appropriate when an underlying invasive cancer is present. HER2 is tested by immunohistochemistry, with in situ hybridization used to confirm borderline results.
Estrogen receptor (ER) and progesterone receptor (PR) — Just under half of cases are positive for these hormone receptors. A positive result may make hormone-blocking therapy appropriate for an underlying hormone receptor-positive cancer.

Because Paget disease is so often associated with a high-grade, HER2-positive underlying cancer, these biomarker results are especially important for planning treatment. You can read more in our article on HER2 in breast cancer.

Pathologic stage of Paget disease of the breast

The pathologic stage of Paget disease of the breast depends on whether an underlying invasive cancer is present. When only Paget disease is found, or Paget disease together with DCIS, the tumor stage is Tis (Paget), where “is” stands for in situ, or non-invasive. When Paget disease is found together with an underlying invasive cancer, the tumor is staged according to that invasive cancer, and the Paget component is noted separately. The staging system used is the TNM system of the American Joint Committee on Cancer (AJCC), 8th edition.

What is the prognosis for Paget disease of the breast?

The prognosis for Paget disease of the breast is determined mainly by the underlying cancer, not by the Paget disease of the nipple itself. When Paget disease is found alone or only with DCIS, the outlook is excellent because the disease is non-invasive. When an underlying invasive cancer is present, the prognosis depends on the features of that cancer, including its size, grade, whether it has spread to the lymph nodes, and its hormone receptor and HER2 status. Because Paget disease is often associated with a higher-grade underlying cancer, evaluating and treating that underlying cancer is the priority.

What happens after this diagnosis?

After a diagnosis of Paget disease of the breast, care is usually coordinated by a team that may include a breast surgeon, a medical oncologist, a radiation oncologist, a pathologist, and a radiologist. The first step is imaging of the breast (mammography and often MRI) to look for an underlying cancer, because the findings shape the treatment plan. The pathology findings guide which options the team considers, rather than dictating a single path.

Surgery — Options include mastectomy (removal of the whole breast) or breast-conserving surgery that removes the nipple-areolar complex together with the underlying tumor. Breast-conserving surgery is usually followed by radiation therapy to the remaining breast.
Lymph node evaluation — When an underlying invasive cancer is present, or when a mastectomy is planned, a sentinel lymph node biopsy may be performed to check whether cancer has reached the nearby lymph nodes.
Systemic therapy — Hormone therapy, HER2-targeted therapy, and chemotherapy may be considered based on the biomarker results and the stage of the underlying cancer.

After treatment, follow-up includes regular examinations and imaging to watch for recurrence.

Questions to ask your doctor

Was an underlying cancer found in the breast beneath the nipple, and if so, what type?
Is the underlying cancer invasive, or is it in situ (DCIS) only?
What is the stage of my cancer?
Was microinvasion seen, and does it change my treatment?
What are my hormone receptor (ER and PR) results?
Is my cancer HER2-positive, and does that change my treatment options?
Do I need additional imaging, such as an MRI, to evaluate the rest of the breast?
What surgical options are available to me: mastectomy or breast-conserving surgery?
Will my lymph nodes need to be checked with a sentinel lymph node biopsy?
Will I need radiation therapy, hormone therapy, HER2-targeted therapy, or chemotherapy?
Should I be referred for genetic counseling to evaluate for an inherited cause such as a BRCA change?
What follow-up and surveillance will I need after treatment?