Encapsulated papillary carcinoma of the breast

by Jason Wasserman MD PhD FRCPC
January 3, 2025

Encapsulated papillary carcinoma is a non-invasive type of breast cancer. “Non-invasive” means that the cancerous cells are confined to where they started and have not spread to nearby breast tissue. This type of tumour behaves similarly to another non-invasive breast cancer called ductal carcinoma in situ (DCIS), which also has a low risk of spreading. Encapsulated papillary carcinoma grows in a way that forms finger-like projections, called “papillae,” inside a cyst-like space. The tumour is surrounded by a fibrous capsule, which helps keep it separate from the surrounding breast tissue. With proper treatment, this tumour generally has a very good outlook.

What are the symptoms of encapsulated papillary carcinoma?

Encapsulated papillary carcinoma may not cause any symptoms in the early stages. When symptoms do appear, they can include a lump in the breast or nipple discharge. However, these symptoms can also be caused by other noncancerous conditions.

What causes encapsulated papillary carcinoma?

The exact cause of encapsulated papillary carcinoma is unknown. Like many other tumours, it likely results from changes in the DNA of breast cells, causing them to grow abnormally.

How is this diagnosis made?

Doctors diagnose encapsulated papillary carcinoma by examining a tissue sample under a microscope. This sample is typically taken through a biopsy, where a small piece of tissue is removed from the lump and studied for signs of cancer. Additional tests, like imaging scans, may also be used to get a clearer picture of the tumour’s size and location.

Microscopic features of this tumour

Encapsulated papillary carcinoma usually has a papillary structure, forming finger-like shapes inside a small, closed space. These structures are made of thin, thread-like stalks that support layers of tumour cells. The tumour has a round shape and is typically surrounded by a capsule.

Under the microscope, the tumour cells appear similar, with oval or round shapes and small to medium-sized nuclei (the central part of the cell that holds DNA). The tumour cells are arranged in single or multiple layers, sometimes forming tiny papillary structures or cribriform patterns, which look like small holes between the cells. Notably, a specific type of cell called a myoepithelial cell, which usually helps distinguish between cancerous and non-cancerous breast conditions, is usually missing in this tumour.

Nuclear grade

Pathologists divide encapsulated papillary carcinoma into three levels or grades: low nuclear grade (grade 1), intermediate nuclear grade (grade 2), and high nuclear grade (grade 3). The nuclear grade is determined by looking at a part of the cell called the nucleus and comparing it to the cells normally found in the breast. They also look for the number of mitotic figures (tumour cells dividing to create new tumour cells).

• Low nuclear grade (grade 1)  – These tumours have small nuclei and few mitotic figures.
• Intermediate nuclear grade (grade 2) – These tumours have larger and more abnormal nuclei and few mitotic figures.
• High nuclear grade (grade 3) – These tumours have very abnormal-looking nuclei and mitotic figures are found throughout the tumour.

The nuclear grade is important because high grade (grade 3) encapsulated papillary carcinoma is associated with a higher risk of developing invasive cancer compared to a tumour with a low nuclear grade (grade 1).

What does encapsulated papillary carcinoma with invasion mean?

Encapsulated papillary carcinoma with invasion means some tumour cells have spread beyond the fibrous capsule surrounding the tumour. When the cancerous cells move outside of this capsule, they can invade nearby breast tissue, which increases the risk that tumour cells will spread to lymph nodes or other parts of the body. This change can affect treatment options, as doctors may recommend additional treatments to help control or prevent the spread of the tumour.

What stage is encapsulated papillary carcinoma?

Encapsulated papillary carcinoma is assigned a stage called Tis. This is the same stage given to ductal carcinoma in situ (DCIS), a non-invasive form of breast cancer. The Tis stage indicates the tumour is in situ, meaning it remains confined within the original location without spreading into nearby tissues. This classification highlights that encapsulated papillary carcinoma is an indolent, or slow-growing, tumour with a very low risk of spreading to other areas.

What is the prognosis for encapsulated papillary carcinoma?

Encapsulated papillary carcinoma generally has a very good outlook, especially if there are no areas of invasive cancer (cancer that has spread beyond the capsule) nearby. In cases with invasion, this tumour can spread to lymph nodes. If ductal carcinoma in situ (another type of non-invasive breast cancer) is present in the surrounding breast tissue, there may be a higher risk of the tumour coming back. The usual treatment for encapsulated papillary carcinoma involves surgically removing the tumour along with some surrounding tissue to check for any spread and to lower the risk of recurrence. If the tumour has certain features, like more varied cell shapes, higher cell activity, or specific markers (triple-negative or HER2-positive), doctors may treat it more like an invasive breast cancer, which may require additional treatments.

About this article

Doctors wrote this article to help you read and understand your pathology report.  Contact us with any questions about this article or your pathology report. Read this article for a more general introduction to the parts of a typical pathology report.

Other helpful resources

American Breast Cancer Foundation

Canadian Breast Cancer Foundation