Breast Cancer In Situ

Ductal carcinoma in situ is a very early form of breast cancer where abnormal cells are found inside the milk ducts but have not spread into surrounding breast tissue. While not immediately life-threatening, understanding this condition and its treatment options is essential for anyone who receives this diagnosis.

DCIS, ductal carcinoma in situ, noninvasive breast cancer, preinvasive breast cancer, stage 0 breast cancer, intraductal carcinoma, ductal intraepithelial neoplasia

Table of contents

• What is ductal carcinoma in situ?
• How common is DCIS?
• Symptoms of DCIS
• Causes and risk factors
• How DCIS is diagnosed
• Understanding grade and stage
• Treatment options for DCIS
• Outlook and survival

What is ductal carcinoma in situ?

• Breast
• Milk ducts

Ductal carcinoma in situ (DCIS) is a very early form of breast cancer where cancer cells are confined inside a milk duct in the breast^[1]. The milk ducts are small tubes that carry milk from the areas where it is made to the nipple during breastfeeding. In DCIS, the abnormal cells have not spread into the breast tissue around the ducts^[2].

DCIS is sometimes called noninvasive, preinvasive, or stage 0 breast cancer^[1]. The term “in situ” means “in place,” indicating that the cancer cells remain where they started and have not invaded nearby tissue^[5]. Unlike invasive breast cancer, where cancer cells have broken out of the ducts and spread into surrounding breast tissue, DCIS cells are all contained inside the ducts^[2].

DCIS is not immediately life-threatening. However, if left untreated, some cases could develop into invasive breast cancer over time^[6]. Research suggests that without treatment, somewhere between 10% to 50% of DCIS cases may progress to invasive breast cancer, though doctors cannot currently predict which cases will progress and which will not^[16].

How common is DCIS?

DCIS accounts for 20% to 25% of all breast cancer diagnoses in the United States^[5]. Around 7,300 women are diagnosed with DCIS in the UK each year^[2], and approximately 59,080 new cases of DCIS will be diagnosed in women in the US this year^[6].

The diagnosis of DCIS has increased significantly since routine mammography screening became widespread. Before screening mammograms were common, less than 5% of newly diagnosed breast cancers were DCIS^[8]. Today, DCIS is detected much more frequently because mammograms can identify it before any symptoms appear^[2].

While DCIS can occur in men, it is extremely rare, accounting for less than 0.1% of cancer diagnoses in males^[5]. Men do not have a breast screening program because DCIS and breast cancer are so uncommon in them^[2].

Symptoms of DCIS

Most people with DCIS do not have any symptoms when they are diagnosed^[1]. DCIS is usually found during a mammogram done as part of breast cancer screening or to investigate a breast lump^[1]. On a mammogram, DCIS typically appears as tiny flecks of calcium in the breast tissue, called calcifications^[1].

A small number of people with DCIS may notice certain changes in their breasts^[2]. These can include:

• A lump in the breast^[1]
• Bloody nipple discharge^[1]
• A rash on the nipple that may be red and scaly^[2]

If you notice any changes in your breasts, it is important to make an appointment with your doctor or other healthcare professional^[1].

Causes and risk factors

The exact cause of DCIS is not fully understood. DCIS happens when healthy cells in the milk duct change and grow uncontrollably, but experts are not sure why these changes take place to begin with^[5].

There is a genetic predisposition in some patients with DCIS, most notably mutations in the BRCA1 and BRCA2 genes^[8]. However, most people with DCIS do not have family members with breast cancer^[5].

Several factors can increase the risk of developing DCIS^[5]:

• A biological family history of breast cancer
• A personal history of breast cancer or atypical hyperplasia (abnormal cell growth)
• Being female
• Being over age 30
• Getting your period before age 12
• Having a baby after age 30
• Having dense breast tissue
• Having gene mutations associated with increased cancer risk (BRCA1 and BRCA2)
• Having previous radiation therapy directed at the breasts or chest
• Never being pregnant or breastfeeding
• Starting menopause after age 55

Having a risk factor does not mean you will definitely get DCIS. Risk factors are about probability—what may increase your chance of developing a condition^[5].

How DCIS is diagnosed

More than 90% of DCIS cases are discovered during mammograms^[5]. A mammogram is an X-ray of the breast tissue used to screen for breast cancer. If a mammogram shows something concerning, your doctor will likely order additional breast imaging and a biopsy^[10].

If an area of concern is found during a screening mammogram, you may have a diagnostic mammogram. This test takes views at higher magnification from more angles than a screening mammogram^[10].

To confirm a diagnosis of DCIS, doctors need to examine tissue from the breast. During a biopsy, a small sample of breast tissue is removed using a needle. This sample is then sent to a laboratory where doctors called pathologists examine it under a microscope^[10]. The pathologist looks at the cells to determine if DCIS is present and what characteristics it has.

Understanding grade and stage

Doctors use the grade and stage of cancer to help decide which treatment is needed^[2]. Grading means how abnormal the cells look under a microscope. Staging means how big the cancer is and how far it has spread^[2].

Grade

DCIS grade is divided into three categories^[2]:

• Low grade (more slowly growing)
• Intermediate grade
• High grade (more quickly growing)

Doctors think that high grade DCIS is more likely to come back after treatment and more likely to spread into the surrounding breast tissue and become an invasive cancer^[2].

Stage

DCIS is considered a preinvasive breast cancer. The cancer cells are in breast ducts and have not started to spread into the surrounding breast tissue^[2]. In the number staging system, which divides cancers into stages 0 through 4, DCIS is stage 0^[2].

In the TNM staging system, which stands for Tumor, Node, Metastasis, DCIS is classified as Tis N0 M0. This means the cancer is still in its original place (Tis), has not spread to lymph nodes (N0), and has not spread to other parts of the body (M0)^[2].

Treatment options for DCIS

Surgery is the main treatment for DCIS^[2]. Because DCIS might progress to invasive breast cancer, and doctors cannot predict which cases will progress, almost all cases are treated^[16]. The goal of treatment is to remove the DCIS and reduce the risk of it coming back or developing into invasive breast cancer.

Surgery

You might have surgery to remove either an area of the breast or the whole breast^[2]. Your surgeon might recommend a particular surgery or give you a choice of operations.

Breast-conserving surgery (also called lumpectomy or wide local excision) removes the area of DCIS and a border of healthy tissue around it^[2]. Many people have this type of surgery because it allows them to keep most of their breast.

Mastectomy removes the entire breast. You might have a mastectomy if the area of DCIS is large or if there are multiple areas of DCIS in different parts of the breast^[2]. Some people prefer to have the whole breast removed because it makes them feel more confident that the DCIS has been removed^[2].

Radiation therapy

After breast-conserving surgery, you might have radiation therapy to the rest of the breast tissue, especially if the DCIS cells look very abnormal (high grade)^[2]. The radiation treatment aims to kill off any abnormal cells that might still be in the breast tissue^[2]. Treatment typically involves three to four weeks of radiation^[13].

Your doctor or breast care nurse will discuss with you the possible benefits and risks of radiation therapy^[2].

Hormone therapy

Some people may receive hormone therapy after surgery and radiation. Hormone therapy is typically taken for five years and can help reduce the risk of the cancer coming back^[13]. However, recent research suggests that in most cases of DCIS, the side effects of hormone therapy may outweigh its benefits^[13].

It is important to discuss your options with your doctor or nurse. You may have different reasons for choosing a particular treatment. The decision should take into account the characteristics of your DCIS, your overall health, and your personal preferences^[2].

Outlook and survival

DCIS is highly treatable, and the outlook is excellent^[5]. Though it can be very stressful and alarming, DCIS is not life-threatening—practically all patients with stage 0 breast cancer can be cured^[6].

The 10-year survival rate for women diagnosed with DCIS is 98% regardless of whether they receive radiation or hormone treatment after surgery^[13]. These treatments do not change survival but instead reduce the risk of breast cancer developing in the future^[13].

Having DCIS can increase the risk of developing invasive breast cancer later. This is why treatment is recommended and why regular follow-up care is important^[6].

If you have received treatment for DCIS, you may have a higher risk of developing other health conditions as you age, including osteoporosis, high blood pressure, and heart disease. To reduce your risk of these complications, ask your healthcare provider how often you should have screenings and follow-ups^[5].