Is breast cancer infectious

Answer 1

Not likely in any feasible method. The best way to put it is that it would be rather difficult to become infected by another individual with cancer. There is a phenomenon called metastasis. Only malignant tumor cells and infections have the established capacity to metastasize. Essentially what occurs is that cancer cells can "break away", "leak", or "spill" from a primary tumor, enter lymphatic and blood vessels, circulate through the bloodstream, and settle down to grow within normal tissues elsewhere in the body. When tumor cells metastasize, the new tumor is called a secondary or metastatic tumor, and its cells are like those in the original tumor. This means, for example, that, if Breast cancer metastasizes to the lungs, the secondary tumor is made up of abnormal breast cells, not of abnormal lung cells. The tumor in the lung is then called metastatic breast cancer, not lung cancer.

Although metastasis only refers to within an individual (i.e. infectious spread of cancer cells within their own body), it is completely conceivable that by taking up the metastatic cancerous cells into a syringe and injecting them into another immuno-compromised individual, that cancer can be spread to that individual. Although this is highly unlikely, it could be spread by shared needles.