Mucinous Carcinoma of the Breast Treatment and Survival

Medically reviewed by Doru Paul, MD

Mucinous carcinoma of the breast, also called colloid breast cancer, is a rare form of invasive ductal cancer. It starts in a milk duct of the breast and spreads to nearby healthy tissues. With mucinous carcinoma, the jelly-like tumor is surrounded by a pool of mucin (the main component of mucus) containing cancer cells.

Most mucinous carcinomas of the breast are estrogen- and progesterone-receptor-positive, meaning that more hormone-based treatments are available. For this and other reasons, mucinous carcinomas are very treatable, and the outlook is usually good with early diagnosis and treatment. Mucinous carcinomas rarely spread to the lymph nodes.

This article describes the symptoms and causes of mucinous carcinoma, including how this uncommon form of breast cancer is diagnosed and treated.

What Are the Symptoms of Mucinous Carcinoma?

Mucinous carcinoma of the breast causes a gelatinous tumor that feels like a slightly bumpy water balloon. A lump may be felt in the breast or under the arm and be soft to the touch

Additional signs and symptoms include:

• Thickening or swelling of the breast

• Change in the size or shape of the breast

• Nipple inversion (pulling in of the nipple into the breast)

• Nipple discharge, sometimes bloody

• Breast dimpling or an orange peel-like skin texture

• Skin redness, peeling, or scaling

• Pain in the breast or nipple (rare)

Smaller tumors may be hard to detect during a breast self-exam. Larger tumors may press on surrounding tissues and cause breast tenderness.

Related: Breast Pain and Breast Cancer

What Causes Mucinous Carcinoma of the Breast?

Mucinous carcinoma of the breast accounts for 1% to 7% of invasive breast cancers. Researchers don’t know what causes it but suspect that hormonal influences (such as estrogen replacement therapy) or certain gene variants (such as BRCA1, BRCA2, or HER2 gene mutations) play a part.

Mucinous carcinoma can affect people of any age but is mainly seen in postmenopausal females over 65. Males can also get mucinous carcinoma of the breast, but this is uncommon.

Additionally, common risk factors associated with all types of breast cancers include:

• Family history of breast cancer

• Giving birth for the first time after age 30

• Prior radiation therapy to the chest

• An unhealthy diet

• Being overweight and/or having a sedentary lifestyle

• Using tobacco products 
  

Mucinous carcinoma may be found near or mixed with other more common types of breast cancers, including ductal carcinoma in situ (DCIS).

The tumors may also contain invasive ductal carcinoma (IDC) cells. If the IDC cells make up more than 10% of the tumor, the cancer is called a mixed mucinous carcinoma. A pure mucinous tumor has at least 90% mucinous cells.

How Mucinous Carcinoma Is Diagnosed

The diagnosis of mucinous carcinoma involves a review of your medical history, a physical exam, and imaging studies. The diagnosis is definitively confirmed with a biopsy and an examination of the tissue sample under a microscope.

The investigation may involve some or all of the following:

• Physical examination: Your healthcare provider will check both breasts and the lymph nodes in your armpits to feel for any lumps or abnormalities. You will also be asked about family history and risk factors for breast cancer.

• Mammogram: A mammogram is often able to detect mucinous carcinoma. However, because it has well-defined edges and pushes against nearby healthy tissues, the mass typically looks like a benign (noncancerous) breast lump on a mammogram. (Other invasive breast cancers appear with irregular borders and calcium deposits, which appear as white specs on mammography.)

• Breast ultrasound: Ultrasound uses sound waves to obtain images of breast tissue and allows healthcare providers to see all sides of the breast. It is possible to see mucinous carcinomas on a breast ultrasound, but, as with mammograms, they may be hard to distinguish from benign lumps.

• Breast magnetic resonance imaging (MRI): A breast MRI can offer clearer images of the breast and check for other types of cancer. An MRI is better able to detect changes in soft tissues and may provide stronger evidence of mucinous carcinoma than a mammogram or ultrasound.

• Breast biopsy: A breast biopsy involves making a small incision and taking samples from the suspicious area for examination under the microscope. Mucinous carcinoma appears as clusters of tumor cells floating in pools of mucin.

How Is Mucinous Carcinoma Treated?

Mucinous carcinoma should be treated to get rid of the cancer and to prevent it from returning (recurrence). Your treatment plan for mucinous carcinoma might include one or more therapies.

Surgery

There are two forms of surgery used for mucinous carcinomas of the breast:

• Lumpectomy: The removal of the tumor and some of the healthy tissues around it.

• Mastectomy: The removal of the entire breast (or both breasts, if necessary)

Research shows the spread of cancer to lymph nodes is uncommon with mucinous carcinoma. Still, to be on the safe side, some surgeons may also opt to do a sentinel node biopsy (removal of one or two lymph nodes closest to the tumor). If there are no cancer cells there, cancer is unlikely to have spread.

Radiation

Following a lumpectomy, your healthcare provider may suggest radiation therapy, which involves sending high-energy rays directly to the affected area of the breast to destroy any remaining cancer.

Cancer cells are more susceptible to radiation than healthy cells, which is the reason they are destroyed. While healthy cells may get damaged with radiation as well, they are able to repair themselves and recover, though you may experience some side effects.

Chemotherapy

Chemotherapy involves taking anti-cancer medications in pill form or intravenously (through a vein). These medicines travel through the bloodstream with a main goal of destroying any cancer cells that have separated from the initial tumor and entered the bloodstream to other parts of the body.

Hormone Therapy

Hormone therapy involves medications, such as tamoxifen, to block or lower the effects of estrogen. Since most mucinous carcinomas are estrogen- and/or progesterone -positive, hormone therapy is likely to be an effective option for treating them. Moreover, hormone therapy lowers the risk of recurrence.

You should discuss all the risks and benefits of treatments with your healthcare provider. Both of you, as a team, are in the best position to determine what might be best for you.

Prognosis

Mucinous carcinoma of the breast is slow-growing. Since it is not aggressive, your prognosis (likely outcome after treatment) is better than that of people with other invasive breast cancers.

According to a 2019 report in Radiology Case Reports, the five-year survival rate for mucinous carcinoma of the breast is 94%, meaning that 94 out of every 100 treated people will live for at least five years. Some live for many years more.

Summary

Mucinous carcinoma of the breast is a rare form of breast cancer that causes a jelly-like tumor surrounded by mucus. These cancers are not aggressive and rarely spread to lymph nodes. The treatment involves surgery accompanied by radiation, chemotherapy, or hormone therapy. The outlook after treatment is good with 94 out of every 100 people living for at least five years.

Read Next: An Overview of Breast Cancer

Read the original article on Verywell Health.