Breast cancer is the most common invasive cancer in women and the second leading cause of cancer death in women after lung cancer. But what is breast cancer? How does it develop?

Breast cancer is an uncontrolled growth of breast cells that can occur due to abnormal mutations or alterations of the genes responsible for regulating cell growth and keeping them healthy. Normally, the cells of our body replace themselves with an orderly process of cell growth: new healthy cells take the place of the old ones. But over time, mutations can “activate” certain genes and “deactivate” others in a cell. That modified cell gains the ability ability to keep dividing without control or order, producing more cells just like it and forming a tumor.

A tumor can be benign (not dangerous to health) or malignant (has the potential to be dangerous). Benign tumors are not considered cancerous: their cells are close to normal in appearance, they grow slowly, and they do not invade nearby tissues or spread to other parts of the body. Malignant tumors are cancerous. Left unchecked, malignant cells eventually can spread beyond the original tumor to other parts of the body.

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Over time, cancer cells can invade nearby healthy breast tissue and make their way into the underarm lymph nodes, small organs that filter out foreign substances in the body. If cancer cells get into the lymph nodes, they then have a pathway into other parts of the body. The breast cancer’s stage refers to how far the cancer cells have spread beyond the original tumor.

There are different ways of staging breast cancer. One way is from stage 0–4, with subdivided categories at each numbered stage. Descriptions of the four main stages are listed below, though the specific substage of a cancer may also depend on other specific characteristics of the tumor, such as HER2 receptor status.

Stage 0: Known as ductal carcinoma in situ (DCIS), the cells are limited to within the ducts and have not invaded surrounding tissues.

Stage 1: At this stage, the tumor measures up to 2 centimeters (cm) across. It has not affected any lymph nodes, or there are small groups of cancer cells in the lymph nodes.

Stage 2: The tumor is 2 cm across, and it has started to spread to nearby nodes, or is 2–5 cm across and has not spread to the lymph nodes.

Stage 3: The tumor is up to 5 cm across, and it has spread to several lymph nodes or the tumor is larger than 5 cm and has spread to a few lymph nodes.

Stage 4: The cancer has spread to distant organs, most often the bones, liver, brain, or lungs.

At in this last stage that our chief scientist Silvia Scaglione and the team of B2B Breast 2 Bone are focused their researches. To shed light on the bone metastatic process, B2B aims to develop a breakthrough technology that for the first time dissects the steps of spontaneous breast cancer metastasis to the bone and captures the 3D complexity of the process.