What is breast cancer?

Breast cancer is a disease in which the uncontrolled multiplication of abnormal breast cells creates a tumor.

Worldwide, it is one of the three most common types of cancer, alongside lung and colorectal cancer, in addition to non-melanoma skin cancer, which is the most common. Considering diagnoses in both sexes, breast cancer cases represent 11.6% of the total. When the breakdown is only among women, this number rises to 24.2%.

In Brazil, breast cancer is the most common cancer in women (excluding non-melanoma skin tumors). For 2023, INCA (National Cancer Institute) estimated approximately 73,610 new cases in the country.

Men can also be surprised by a breast cancer diagnosis, but the incidence is very low: approximately 1% of all cases.

Breast Cancer Subtypes

Breast cancer is comprised of different subtypes, making the disease extremely heterogeneous. It can evolve in different ways, and treatment is also quite diverse. The most common types are:

Ductal Carcinoma In Situ – This is the most common type of cancer, and it does not invade the adipose tissue (fat) surrounding the breast ducts. It can progress to invasive cancer, although this is unlikely to occur if the disease is adequately treated. It generally does not affect axillary lymph nodes and has no potential for metastasizing to other organs.

Invasive Ductal Carcinoma – This represents between 65% and 85% of invasive breast cancer cases. It begins in the breast ducts, crossing the duct membrane barrier and invading the adipose tissue (fat) surrounding the breast ducts. It can invade adjacent breast structures, such as the axillary lymph nodes, or even cause metastases to other organs;

Invasive Lobular Carcinoma – represents about 10% of breast cancer cases. It originates in the milk-producing glands – the mammary lobules – and can develop locally, in addition to having the potential to present as multicentric disease (in more than one location in the breast) or invade adjacent tissues, such as the axillary lymph nodes, or even cause metastases to other organs;

Lobular Carcinoma In Situ – is an uncommon histological type and represents only 2% to 6% of cases. It also originates in the mammary lobules and does not have the ability to invade tissue. However, it can be a precursor to invasive breast cancer.

Less common types of breast cancer include:

Inflammatory carcinoma – uncommon, representing 1% to 3% of cases. The lymphatic ducts in the skin overlying the breast tissue are blocked and invaded by tumor cells. The lymphatic system acts as a defense against infection and inflammation, triggering a chain reaction that causes the characteristic inflammatory appearance of the breast.

Paget's disease – extremely rare, with an incidence of 0.5% to 4% of breast cancer cases. It begins in the mammary duct, affecting the skin of the nipple and areola. It can be asymptomatic or manifest as crusting and inflammation on the nipple.

Phylloid tumor – very rare, it develops in the connective tissue of the breast (stroma), while others develop in the ducts or lobules.

Angiosarcoma – begins in the cells lining the blood vessels or lymphatic vessels.

Symptoms and Signs of Breast Cancer

Breast cancer has symptoms that can be noticed during a woman's self-examination or during routine appointments with her gynecologist. In most cases, the symptoms are:

A fixed, usually painless lump or nodule, present in about 90% of cases where cancer is self-noticed;

Redness of the breast skin, which may or may not be accompanied by retraction and an orange-peel appearance;

Changes in the nipple, such as retraction or inversion;

Small lumps in the armpits or neck;

Spontaneous and abnormal discharge from the nipples, including bloody discharge.

Self-examination can be performed in the shower, while changing clothes, or in any other daily situation, whenever the woman feels most comfortable. Both breasts and nipples should be palpated for small breast changes. The earlier a breast cancer is detected, the greater the chance of a cure. Without a doubt, self-examination can contribute to early diagnosis of the disease.

Breast Cancer Diagnosis

Breast cancer diagnosis is based on a three-pronged approach consisting of a clinical examination, imaging tests, and histopathological analysis.

After a medical history taken by a specialist, appropriate imaging tests are required to evaluate the breast parenchyma, including breast ultrasound and mammography. Breast MRI can complement or help in specific situations. If breast cancer is suspected, a biopsy of the region is necessary to confirm—or deny—the diagnosis.

The main breast biopsy methods are core biopsy, or core needle biopsy, and mammotomy, or biopsy.