What Is Mucinous Carcinoma?

Mucinous carcinomas are cancer cells which form in mucin, the main component of mucus. Healthy cells depend on mucin to function properly, and cancer cells become encased in mucin in mucinous carcinomas.¹ It is most common in breast cancer but can also occur in ovarian cancer, lung cancer, rectal cancer, uterine cancer, and colon cancer.

This article will discuss mucinous carcinomas by looking at mucinous carcinomas of the breast in more depth. The article will explore the following subtopics: how common mucinous carcinomas are, what the signs and symptoms of mucinous carcinomas are, how they are treated, and frequently asked questions. 

Introduction

Mucinous carcinoma of the breast is a relatively rare type of breast cancer, accounting for about 2% of all breast carcinomas. According to the latest WHO breast tumour classification, mucinous carcinoma is classified as a special type of breast cancer. Based on tumour cells, mucinous carcinomas are divided into two subtypes:

• Mucinous carcinoma alone - consists of tumour tissue with mucus production in more than 90% of tumours.
• Mixed type of mucinous carcinoma - tumour tissue forms without mucus.² 

How common is mucinous carcinoma?

Between 1-2% of breast cancer cases are mucinous cancers. Typically, it affects older women and grows slowly.³

What are the signs and symptoms of mucinous carcinomas?

There are several similarities between mucinous breast cancer and other kinds of breast cancer, such as

• Breast tissue that is thickened or lumped
• The skin's texture changes, such as puckering or dimpling
• Underarm lumps or swellings
• The nipple has changed
• The nipple discharges
• Breasts that have changed in size or shape

What are the treatment options for mucinous carcinoma?

A variety of treatments are available for mucinous breast cancer, depending on its characteristics (such as size, grade, and hormone receptor status).⁴ 

As with all types of breast cancer, the treatments offered will depend on the feature characteristics of the mucinous breast cancer mentioned above. The goal of the treatment is to remove the cancer and reduce the risk of it coming back or spreading to other parts of the body.

Surgery is usually the first treatment for mucinous breast cancer, and the type of surgery recommended depends on:⁵

• Where the cancer is in the breast
• The size of the cancer relative to the size of the breast
• Is there more than one tumour? in the affected area?  

There are two main types of surgery

A lumpectomy is the removal of the cancer with a portion of normal breast tissue around it.⁶ Sometimes, more surgery is needed if the portion of normal tissue surrounding the lump that was removed during the first operation is not clear. In the eventuality that the cancer has not been removed, more surgery will need to be performed. This second operation may need to be a mastectomy, which is the removal of all the breast tissue, including the nipple area.⁷

The health specialist will want to check if any of the lymph nodes under the arm contain cancer cells. This helps them decide whether they will benefit from any additional treatment after surgery in case the cancer has spread to other parts of the body.

After surgery, further treatment, called adjuvant treatment, may be required and can include the following:

• Chemotherapy
• Radiotherapy
• Hormone (endocrine) therapy
• Targeted (biological) therapy 
• Bisphosphonates 

The goal is to reduce the risk of breast cancer returning in the same breast or spreading elsewhere in the body. Mucinous breast cancer is less likely to spread to the lymph nodes than most other types of breast cancer. This is particularly the case if the cancer is small or if it’s pure mucinous breast cancer. 

Most women who have a mastectomy will be offered the option to have breast reconstruction. However, in other cases, an artificial breast prosthesis can be another option to use inside the bra to restore the shape of the breast.

Summary

Mucinous carcinoma of the breast can be subdivided into two specific types: pure and mixed. Symptoms are similar to other types of breast cancer. There are several treatment options available, including surgery followed by secondary treatment to ensure the cancer is in remission.

FAQs

What questions should I ask the doctor?

If you are diagnosed with a lump, ask what the next steps are and the tests that need to be taken to specify whether the type of mucinous carcinoma is pure or mixed.

Discuss the best treatment options available after confirmation of the diagnosis.

What risks does each of the treatment options carry, and what are the chances of the cancer returning?

How is mucinous carcinoma diagnosed?

Mucinous breast cancer is diagnosed using a range of tests. These may include:

• Breast imaging (mammogram)
• Ultrasound scans (images produced by sound waves)
• Core biopsies involve taking a piece of breast tissue and examining it under a microscope with a hollow needle.
• Breast and sometimes lymph nodes are aspirated with fine needles and syringes to obtain cells for examination under a microscope.

What are the risks of treatment for mucinous carcinoma?

Some risks include the following:

• Bleeding from surgical removal of breast tissue
• Infection
• Pain
• Swelling around the area of tissue
• Scarring of tissue
• Blood clots

What is the prognosis for mucinous carcinoma?

Diagnosis and classification of mucinous breast carcinomas are mainly based on histopathological examination. Mucinous breast cancer carries a favourable prognosis with a low recurrence rate and a low incidence of lymph node metastasis.