Welcome to part 2 of the Science 101 series.

Today’s topic is Cancer.

Cancer is one of the most common subjects we see come up in the news, yet it’s also the most complicated. See, cancer is not actually a disease, rather it’s a group of diseases. In fact, cancer is really just another term for a tumor, an abnormal growth of tissue mass (i.e. a “bump”). Specifically, tumors come in two varieties: malignant and benign. The difference is that benign tumors are unable to metastisize (a fancy way of saying “spread”) and invade other parts of the body. Accordingly, a malignant tumor is a cancerous mass that has metastisized. This usually spells out “end game” for the patient, because it’s nearly impossible to rid the body of cancer once it has spread to multiple tissues.

So if cancer describes a group of diseases, how do we differentiate between them? Cancers are named based upon the tissue and cell type it is thought to have originated from. The first step is to define the cell type of origin, by classifying them into one of the various “-omas”. For example, a carcinoma is a cancer derived from epithelial cells, the cells that make up your skin and the inside surfaces of your organs. Another type is a lymphoma, which is a cancer derived from the hematopoietic (blood-producing) cells found within your bones. Then you’ve also got your sarcomas and blastomas. To make things extra complicated, scientists further lengthen this classification by naming the organ from which the cancer is thought to originate. For example, a cancer that started in the liver would be known as a hepatocarcinoma, while the most common type of breast cancer is called a mammary ductal carcinoma since it originates in the breast ducts.

So why do people get cancer? That’s a really tough question that scientists have been debating for quite some time now. For example, environmental factors, those derived from lifestyle choices (like habitual smoking) obviously play a big part. But at the same time, cancer is a disease of erroneous gene expression. Thus genetic factors, simply the nature of your personal DNA sequence, must also play a role. Unfortunately, how much each factor contributes to the onset of cancer changes from person-to-person. This makes it near impossible to pinpoint the root causes of cancer, and has hindered cancer research for quite some time now.