Cancer unlike many other diseases cannot be known with bare eyes or by mere looking at you. Cancer is not a pathogen in itself that infects the hosts and gets transmitted from one host to another. It is more correct to picture a cancer as an internal mistake of the body rather than as an external attack to our body.
For these evidence-based reasons, nobody can know that you have cancer by simply looking at you; there must be a diagnosis.
Cancer is nearly always diagnosed by an expert who has looked at cell or tissue samples under a microscope. In some cases, tests done on the cells’ proteins, DNA, and RNA can help tell doctors if there’s cancer. These test results are very important when choosing the best treatment options.
Tests of cells and tissues can find many other kinds of diseases, too. For instance, if doctors are not sure a lump is cancer, they may take out a small piece of it and have it tested for cancer and for infections or other problems that can cause growths that may look like cancer. The procedure that takes out a piece of the lump, or a sample for testing is called a biopsy.
The tissue sample is called the biopsy specimen. The testing process is sometimes referred to as pathology.
Lumps that could be cancer might be found by imaging tests or felt as lumps during a physical exam, but they still must be sampled and looked at under a microscope to find out what they really are. Not all lumps are cancer. In fact, most tumors are not cancer.
There are so many lab tests that doctors rely on to diagnose a cancer. Such as imaging procedures like: mammogram, CT scan, ultrasound, Magnetic Resonance Imaging (MRI), PET scan, X-rays, biopsy, and many others.