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Symptoms and Diagnosis of Medullary Carcinoma of the Breast

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In this section you can learn about how medullary carcinoma of the breast is detected and diagnosed.

Signs and symptoms

Like other types of breast cancer, medullary carcinoma may not cause any symptoms at first. Over time, a lump can form, and it may be soft and fleshy or somewhat firm to the touch. Most medullary carcinomas are small — less than 2 cm in size. Medullary carcinoma also may cause pain, swelling, redness, or tenderness in the breast.


Tests that obtain images of the tissue inside the breast, such as mammography and ultrasound, sometimes can find a medullary carcinoma. On these tests, medullary carcinoma appears as a small, well-defined lump. However, some research suggests that mammography is not reliable at detecting medullary carcinomas. One study showed that these cancers were more likely to be found during self-examination or examination of the breasts by a doctor.

Diagnosing medullary carcinoma usually involves a combination of steps:

  • A physical examination of the breasts. Your doctor may be able to feel the lump in the breast.
  • A mammogram to locate the tumor and check for evidence of cancer in other areas of the breast.
  • Ultrasound to obtain additional images of the breast and check for other areas of cancer.
  • Biopsy to remove some or all of the lump to look at it under the microscope. A few cells from the lump can be extracted using a special needle, or the lump can be removed through a small incision. Biopsy is the key to accurate diagnosis, because imaging tests alone can’t tell the difference between medullary carcinoma and other types of breast cancer.

When looked at under a microscope, medullary carcinoma has a number of important features that a pathologist looks for:

  • A clear, well-defined boundary between tumor tissue and normal breast tissue. Medullary carcinoma pushes against the surrounding healthy tissue, but doesn’t grow into it in the same way invasive ductal carcinoma usually does.
  • Large-sized cancer cells with a high-grade appearance, meaning that they look very different from normal, healthy breast cells. However, medullary carcinoma cells do not behave like high-grade cancer cells, which are aggressive and grow and spread quickly. Medullary cancer cells also tend to blend together in a distinctive “sheetlike” pattern; it’s hard to see each cell’s individual membrane (outer lining).
  • Immune system cells (white blood cells called lymphocytes and plasma cells) at the edges of the tumor. Immune system cells work to fight off diseases and any substances they see as a threat to the body. It’s believed that these cells help keep the medullary carcinoma in check, preventing it from growing and spreading quickly.

If the tumor has all of these features, it is considered to be a “true” medullary carcinoma. Sometimes the tumor has only some of these features but not others, or there may be some invasive ductal carcinoma cells mixed in. In these cases, your doctor may call the tumor “atypical medullary carcinoma.”

In addition, medullary carcinoma cells often express a protein called p53. The pathologist may test for p53 to help decide if the cancer is truly medullary.

There are some other key features of medullary carcinoma:

  • Hormone-receptor-negative: Medullary carcinoma usually tests negative for hormone receptors.
  • HER2-negative: Medullary carcinoma also usually tests negative for receptors for the protein HER2/neu.

Diagnosing medullary carcinoma can be challenging. It may be hard to tell the difference between medullary carcinoma cells and cells that make up a usual invasive ductal carcinoma. If you receive a diagnosis of medullary carcinoma, ask your doctor whether the pathologist who looked at the sample has experience diagnosing this type of cancer. You also may want to get a second opinion from another hospital pathology lab.

For more information about how breast cancer is diagnosed, see Your Diagnosis.

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