What Is Breast Cancer?

Breast cancer is the most common invasive disease in female patients. More than 1 out of every 8 women in the US will develop the disease during their lifetime, according to BreastCancer.org, and around American 2.8 million women currently have a history of breast cancer, including those who have completed treatment.

Carcinomas Of The Breast

Breast cancer usually begins in the thin ducts that carry milk to the nipple. This form of the disease is called ductal carcinoma. Far less common are lobular carcinomas, cancers that begin in the lobules, the glands that actually produce milk.

In Situ: When Cancer Stays Put

Nearly 1 out of every 5 breast cancer diagnoses are for ductal carcinoma in situ, which means the cancer hasn’t yet spread beyond the duct cells in which it began. This is the earliest point at which breast cancer can be detected, so early that it’s classified as stage 0 breast cancer.

MammogramWhile the disease can present some symptoms at this very early stage, it usually doesn’t, and most malignancies in situ (around 80%, according to WebMD) are identified on routine mammogram screenings. When a carcinoma in situ does present symptoms, they often include breast pain and a bloody or yellowish discharge from the nipple, but again, those signs are rare.

But if we can catch the disease at this very early stage, a patient’s prognosis is quite favorable. An estimated 20% of women are diagnosed with breast cancers in situ, tumors confined to their site of origin, and the five-year survival rate at this point is an extremely high 98.8%.

Treatment usually includes a lumpectomy, a sort of scaled-down version of mastectomy in which surgeons remove only the tumor and a little surrounding tissue, and targeted radiation therapy. This treatment is fairly standard, although the extent of radiation will vary depending on the size of the tumor and how much healthy tissue is observed around it.

Invasive Carcinomas

When we think about breast cancer, though, we tend to think of invasive ductal carcinomas, not in situ stages of the disease. Around 80% of the breast cancers diagnosed are spotted at this stage, after the initial malignancy has spread, reaching out from the milk duct in which it began and growing into surrounding tissues.

Invasive ductal carcinomas, or IDC, cause the hallmark symptom of breast cancer, the symptom which many people come to equate with breast cancer in general: a hard, irregularly-shaped lump in the breast. In most cases, lobular carcinomas don’t create lumps, but a thickening or fullness in the breast that’s distinct from the surrounding tissue.

Lumps & Self-Exams

Of course, not all lumps are cancerous; other growths, like cysts and fibroadenomas, can be perfectly benign. In actuality, lumps are fairly common; many women have breasts that just feel lumpy, and breast tissue itself has a naturally bumpy texture.

More than lumps, what you’re looking for in a self-exam are changes in the way your breasts feel over time, and differences between the tissues in either breast. This can be a hard nuance for some patients to understand, and self-exams have not proven the effective early detection method we once hoped they would become.

In fact, the largest review of studies on the subject (abstract at PubMed) found that women who performed routine self-exams probably didn’t benefit from their rigorous surveillance. At the least, breast self-exams didn’t save any lives; there was no difference in overall mortality between women who performed self-exams and women who didn’t.

False positives, on the other hand, increased drastically, almost double among women who routinely checked their breasts for lumps. This led to nearly twice as many unnecessary biopsies. But biopsy isn’t the problem. Analyzing samples of breast tissue under a microscope is really the only way to conclusively diagnose invasive ductal carcinoma.

When Breast Cancer Spreads

Once an initial diagnosis has been confirmed, additional tests, like CT scans and MRIs, are usually performed to figure out whether or not malignant cells have spread even further.

Particular focus is placed on the lymph nodes in a patient’s breasts and underarms, which, in most cases, will be the first places to which breast cancer spreads. That’s a real problem, since the lymphatic system acts very much like a circulatory system, and can quickly ferry malignant cells to other regions of the body, most commonly the bones, lungs, liver or brain, in a process known as metastasis.

Breast Cancer Metastasis To Liver

A breast cancer metastasis in the liver.

Only 5% of women in the US are initially diagnosed with metastatic breast cancer, malignancies that have already spread to organs distant from the breasts. Far more common is “distant recurrence,” when cancers crop up somewhere else after a patient has been completely treated for earlier stages of the disease.

First-line treatments usually include a surgical procedure, either lumpectomy or mastectomy depending on the tumor’s size and how far it’s spread, followed by radiation therapy and / or chemotherapy.

Rare Forms Of Breast Cancer

As we’ve seen, the vast majority of breast cancers originate in either the glands that produce milk or the ducts that transport milk. Sarcomas, which begin in the breast’s connective tissue, are exceedingly rare, accounting for less than 1% of breast cancer diagnoses, according to Johns Hopkins University.

Inflammatory Breast Cancer

Between 1% and 3% of breast cancers are known as inflammatory breast cancer, because they cause symptoms that closely resemble inflammation. The breast will become red and unusually warm, often enlarging and taking on the pitted appearance of a citrus peel, but there usually won’t be any single lump or detectable tumor. It’s not inflammation that’s causing the reaction, though, although inflammatory breast cancers are often mistaken for infections at first sight, and ineffectively treated with antibiotics. Instead, cancer cells have come to block the lymphatic vessels that drain fluids from the breast, causing localized swelling.

Inflammatory breast cancers (IBC) are hard to treat, mainly because they’re hard to diagnose early. Without an identifiable tumor or lump, this form of the disease can easily be missed on a mammogram. IBC is also more aggressive than common carcinomas, and it’s never considered an early-stage cancer since, by definition, the disease has already grown into surrounding tissues.

Treatment can be aggressive, too, although it normally follows a different order than the standard used to tackle most ductal or lobular carcinomas. Instead of opting for surgery first, most doctors will suggest a round of chemotherapy as the starting point, hoping to shrink the cancerous growth as much as possible. After systemic chemo, surgeons will attempt to remove the remaining tumor cells from the breast, followed by a regimen of localized radiation.

Paget’s Disease

Very rare, and almost always accompanied by a ductal carcinoma (either in situ or invasive) deeper in the breast, Paget’s disease of the nipple is a form of cancer that comes to involve the skin of the nipple and, in most cases, the areola.

While researchers aren’t certain what causes Paget’s disease (not to be confused with Paget’s disease of the bone, vulva and penis, all conditions named after the 19th century British doctor who first described them), the going theory is that cancer cells from a deeper tumor are able to travel through milk ducts, thus spreading to the nipple.

Under a microscope, these cancer cells look very distinct, larger and rounder than their healthy neighbors:

Paget Cells

Copyright © 2011 Michael Bonert. Permission is granted to copy, distribute and/or modify this image under the terms of the
GNU Free Documentation License Version 1.2 or any later version published by the Free Software Foundation.

But prior to a full biopsy, Paget’s disease is routinely mistaken for benign skin rashes due to its non-specific symptoms, like itching, redness or flaking.