Medullary carcinoma of the breast is a subtype of invasive ductal carcinoma. It is a type of breast cancer that begins in the milk ducts. This breast cancer is named because the tumor resembles the part of the brain known as the medulla. Medullary carcinoma of the breast represents an estimated 3 to 5 percent of all diagnosed breast cancer cases.

Medullary carcinoma is usually less likely to spread to the lymph nodes and more responsive to treatment than the more common types of invasive breast cancer. Detecting it at its earliest stages can improve prognosis and ideally reduce the need for additional treatments beyond removing the tumor itself.

Sometimes medullary carcinoma may cause few symptoms. A woman may first notice a lump in her breast. Medullary carcinoma of the breast tends to have rapidly dividing cancer cells. Therefore, many women may identify a mass in their breast that can range in size. The lump tends to be either soft and fleshy, or firm to the touch with defined borders. Most medullary carcinomas are less than 2 centimeters in size.

Some women may experience other symptoms related to medullary carcinoma, including:

  • breast tenderness
  • pain
  • redness
  • swelling

If you’re experiencing any of these symptoms, you should see a doctor.

Traditionally, cancerous tumors of the breast can have a hormonal influence. Medullary carcinoma of the breast, however, is usually not hormone influenced. Instead, a woman experiences a change in the genetic makeup of the cells in her breast. This causes the cells to grow uncontrollably (cancer). Doctors don’t know exactly why these mutations occur or how they are related to medullary carcinoma of the breast.

Some women with a genetic mutation known as the BRCA-1 gene are at greater risk for being diagnosed with medullary carcinoma of the breast, according to Johns Hopkins Medicine. This gene tends to run in families. Therefore, if a woman has a history of breast cancer in her close family members, she is at greater risk for the disease. However, if a woman has this gene, this does not necessarily mean she will get medullary carcinoma of the breast.

The average age at diagnosis for medullary carcinomas is between 45 and 52 years. This tends to be slightly younger than women diagnosed with medullary carcinomas, who are diagnosed at age 55 or older.

A doctor can evaluate different treatment options for medullary carcinoma. They will take into account the tumor’s size, the cell type, and if the tumor has spread to nearby lymph nodes. Because the tumors are traditionally less likely to spread, some doctors may recommend removing the tumor only and not pursuing any further treatments. This is true when the tumor is “pure medullary” and only has cells that resemble medullary carcinoma.

However, a doctor may also recommend removal of the tumor as well as other types of cancer treatments. This is true when the cancer may have “medullary features.” This means some cells look like medullary carcinoma where others look like invasive ductal cell carcinoma. A doctor may also recommend additional treatments if the cancer has spread to the lymph nodes. These treatments could include chemotherapy (medicines to kill fast-growing cells) or radiation.

Some medications traditionally used to treat breast cancer do not usually work well on medullary carcinoma of the breast. This includes hormone-related therapies such as tamoxifen or aromatase inhibitors. Many medullary breast cancers are “triple-negative” cancer. This means the cancer does not respond to the hormones progesterone and/or estrogen or another protein known as the HER2/neu protein.

Because medullary carcinoma of the breast is very rare, doctors may have a hard time initially diagnosing the specific cancer type. They may identify a breast lesion on a mammogram, which is a special type of X-ray imaging used to examine the breast. The lesion is usually circular or oval in shape and does not have well-defined margins. A doctor may also order other imaging studies. These can include an ultrasound or a magnetic resonance imaging (MRI) scan.

Medullary carcinomas of the breast can be unique to diagnose. Sometimes, a woman may be more likely to identify a cancerous lesion through feel, than what can be seen on an imaging study. For this reason, it’s important that a woman conduct monthly breast self-examinations, where she feels her breast tissue and nipple for lumps.

If a doctor identifies a lump by touch or imaging, they may recommend a biopsy of the lump. This involves removing cells or the lump itself for testing. A doctor who specializes in examining cells for abnormalities is known as a pathologist. A pathologist will examine the cells under a microscope. Medullary cancer cells also tend to have a p53 genetic mutation. Testing for this mutation may lend support to a diagnosis of medullary carcinoma, though not all medullary cancers have the p53 mutation.

The five-year survival rates for medullary carcinoma of the breast tend to be anywhere from 89 to 95 percent. This means that five years after diagnosis, anywhere from 89 to 95 percent of women with this cancer type are still living.

Medullary carcinoma of the breast tends to respond better to breast cancer treatment than other types of invasive ductal carcinomas. With early detection and treatment, prognosis and survival rates are favorable.