Of the many types of breast cancer, one of the most rare and trickiest to treat is metaplastic carcinoma. Relatively little is known about how it forms or its long-term prognosis.

Metaplastic breast cancer is a form of invasive ductal cancer, meaning that it forms in the milk ducts and then moves into other tissues of the breast. Inside the tumors of this type of cancer are cells not normally found inside the breast, such as squamous (skin) or osseous (bone) cells.

It is also known as carcinoma with metaplasia, or simply metaplastic breast cancer.

Metaplastic sounds very much like metastatic, a more common cancer term, but the two have very different meanings. Metaplastic comes from the Greek phrase for "changed in form,'' which is why it is used to describe cells that appear to have changed into those of another part of the body. Metastatic comes from the Greek phrase for "changed in place,'' describing cancer that has spread from its original site to other areas.

What Are the Symptoms?

Some women with metaplastic breast cancer show no symptoms at all and are identified through routine screening. For others, the symptoms are essentially the same as for other types of breast cancer:

• Lumps or thickening in the breast that were not there before
• Tenderness, discharge or change in appearance of the nipple
• Changes in the appearance of breast skin: redness, scaling, puckering or dimpling
• Irritation of the breast, including redness, swelling and rash
• Unexplained pain in the breast, especially with any of the above symptoms

How Is It Diagnosed?

A number of imaging procedures can be used to determine whether cancer is present. These include:

• Diagnostic mammography. This is much like your routine screening mammogram, except that diagnosing cancer (rather than just checking for cancer) requires more images to be taken and examined.
• Ultrasound. This uses high-frequency sound waves to produce images of breast tissue. These images help doctors to determine whether a lump in the breast is a fluid-filled cyst or a solid tumor.
• Magnetic resonance imaging (MRI). This uses magnetic fields to produce images of the inside of the body.
• Computed tomography (CT or CAT) scan. This creates multiple "slice by slice" pictures of the inside of the body, then combines them into a detailed cross-section picture that can show the presence of tumors.

How Is It Treated?

Because it is so rare, a tried-and-true course of action for metaplastic breast cancer is not readily available. Still, as with all cancer, treatment is at first guided by:

• the size and location of the tumor
• whether the cancer has spread
• the patient's overall health, age, etc.

With these questions in mind, the first step is usually surgery to remove the visible tumor. From there, the following results from the biopsy can help determine further action:

• Testing for hormone receptivity.This helps determine whether the cancer cells will respond well to hormone therapy, such as Tamoxifen, as a treatment option. These drugs work by inhibiting the estrogen receptors on precancerous cells, as estrogen has been linked to breast cancer growth.
• Testing for HER-2 protein.This protein is overproduced in about one fourth of all breast cancers. If this protein is found in a biopsied tumor, then treatment with Herceptin (trastuzumab) may be an option. FDA-approved in 1998, Herceptin binds to the HER-2 protein on cancer cells, enabling the body's own defenses to clear the cancer .

Additional treatments may include chemotherapy and radiation. The diagnostic procedures described above may be repeated to determine whether the cancer has spread.