Medullary breast carcinoma is a rare subtype of invasive breast cancer. The term medullary refers to the tumor's soft, fleshy appearance, which resembles the soft gray matter in the brain stem, called the medulla.

Invasive ductal carcinoma (IDC) is the most common type of breast cancer, accounting for 8 in 10 cases of breast cancer. Medullary breast carcinoma is a rare type of IDC, representing 3–5% of all breast cancer diagnoses.

Continue reading this article for more information on medullary breast carcinoma, including its symptoms, causes, treatment, and survival rates.

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Medullary breast carcinoma accounts for 3–5% of all breast cancer diagnoses.

Medullary breast carcinoma is a type of invasive cancer. It spreads from its original location in the milk ducts in the breast into the surrounding breast tissue.

Medullary breast carcinoma is a rare subtype of IDC that behaves differently than other types of ductal breast cancer.

Although medullary tumors appear highly aggressive, they grow slowly and rarely spread to the lymph nodes.

Plasma and specialized white blood cells called lymphocytes surround medullary breast carcinoma tumors. The presence of these cells may prevent cancer cells from growing and spreading to the surrounding breast tissue.

People can develop medullary carcinoma at any age, but it usually affects women in their late 40s to early 50s. Additionally, this form of breast cancer is more prevalent in Japan than in the United States.

Similar to other types of breast cancer, medullary breast carcinoma may not cause noticeable symptoms in the early stages. Over time, though, a lump can grow large enough for a person to feel it during a breast self-examination.

If symptoms do occur, they can include:

Although hormones play a role in the development of other types of breast cancer, they do not appear to influence medullary carcinomas.

People develop medullary carcinoma as a result of genetic mutations. Those who have a mutation in the BRCA1 gene may have an increased risk of developing medullary breast carcinoma.

According to a 2017 article, medullary breast carcinoma develops in up to 19% of people who carry the BRCA1 gene mutation.

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A doctor may recommend a surgical procedure to remove the tumor.

Early detection can lead to better, more effective treatment. However, medullary breast carcinoma cells look similar to IDC cells, making accurate diagnosis difficult.

There are several effective treatment options for medullary breast carcinoma. The best treatment option varies from person to person, depending on several factors, such as:

  • the type of cell in the tumor
  • tumor grade
  • hormone receptor status
  • lymph node involvement

A doctor may recommend removing the tumor using a surgical procedure, such as a lumpectomy or a mastectomy.

As medullary breast carcinomas are less likely than other cancers to spread to the lymph nodes, a doctor may decide to use surgery without any additional, or adjuvant, treatments, such as chemotherapy or radiation therapy.

Other doctors may recommend a combination of surgery and one or more adjuvant treatments, especially if the cancer cells indicate IDC or have spread to surrounding breast tissue or nearby lymph nodes.

Medullary carcinomas that test negative for hormone receptors will not respond to hormone therapy. Systemic treatments for medullary carcinoma include:

  • chemotherapy, which uses cytotoxic drugs to kill cancer cells
  • radiation therapy, which uses high energy X-rays to destroy cancer cells
  • targeted therapy, which uses specialized drugs that target proteins in cancer cells to prevent them from growing

In general, the outlook for people with medullary breast carcinoma is good because this cancer grows slowly, and there is a low chance of it spreading beyond the breast tissue.

One 2016 study looked at the survival rates for regular and atypical medullary breast carcinoma among 3,688 people. The researchers reported a 5-year survival rate of 89–92% and a 10-year survival rate of 85–87%.

People with medullary breast carcinoma who receive an accurate diagnosis and timely treatment typically have a positive outlook. The disease tends to respond better to treatment compared with other forms of IDC.

Medullary breast carcinoma is a rare type of IDC breast cancer that develops in the milk ducts. Unlike similar types of breast cancer, medullary breast carcinoma grows slowly and presents a low risk of involving the lymph nodes.

In general, medullary breast carcinoma has a high survival rate, and people with this condition have an excellent long-term outlook. Early diagnosis and treatment can improve prognosis and potentially remove the need for adjuvant therapies.