Our first two monthly Glossary Blogs this year tackled “meaty” topics, CAR T-cell Therapy and Tumor Sequencing.
This month, we wanted to “step-back” and tackle a question that had been brought to our attention, that seemed to be, perhaps, the most basic and fundamental term/concept for this community: Is a brain tumor, brain cancer? Or, are brain tumors cancerous?
Simple enough, right? A simple “Yes” or “No” answer should do, right?
Well, not exactly. Which has caused some confusion and debate in the community.
Let’s take a deeper look.
First, some definitions…
- Malignancy/Malignant – Tending to be severe and become progressively worse, or (in regard to a tumor), having the properties of a malignancy that can invade and destroy nearby tissue and that may spread (metastasize) to other parts of the body.
- Metastasize/Metastases/Metastatic – Having to do with metastasis, which is the spread of cancer from the primary site (the place where it started) to other places in the body.
Quick Brain Tumor Overview
A brain tumor is an abnormal growth of cells that form a mass in the tissue of the brain.
Tumors that start and develop directly in the brain or spinal cord are called primary brain or CNS tumors. A tumor that starts in another part of the body and spreads to the brain is called a “metastatic,” or “secondary,” brain tumor (also often called brain metastases and sometimes just “brain mets”).
*For the purpose of the remainder of this discussion, we’ll be focusing on primary brain tumors.
Benign vs. Malignant Tumors
Brain tumors can be classified as either “benign” (non-malignant/non-cancerous) or “malignant.” Malignant is a term that typically implies, and refers to, cancer. And, in fact, the term often has become a stand-in for “cancer.” The terms are often used interchangeably.
Both benign and malignant tumors disrupt normal brain function, cause signs and symptoms, and typically require treatment of some sort.
The biggest difference between “benign” and “malignant” tumors is that malignant tumor cells are much more aggressive and have more of an ability to grow rapidly and spread into otherwise healthy brain and spinal tissue. Benign tumors typically have “well-defined” or clear borders, which means they are well-contained or encased, while malignant tumors typically invade and comingle with healthy tissue and cells. (More on each below).
Now, here is where the question above, and some more confusion, comes into play…
Because of the uniqueness of the brain as an organ, and subsequently the uniqueness of tumors arising in the brain (primary brain tumors), brain tumors are somewhat distinct in how they are categorized when it comes to the concepts of “cancer” and “malignancy,” when compared to tumors and cancers of other organs.
With this in mind, let’s apply these terms to brain tumors:
- Primary brain tumors that are classified as “benign” are not cancerous. However, benign brain tumors can be considered dangerous and/or life-threatening if they are located in areas of the brain that control vital functions like breathing. A benign tumor will not spread to other parts of the body, but that does not mean that it is harmless.
- Primary brain tumors that are classified as “malignant” are typically considered cancerous, or brain cancer. We emphasize the word “typically,” because not all doctors agree** that primary malignant brain tumors are always necessarily “brain cancer.” This is because, again, they are not known to metastasize, or spread, to other parts of the body outside the Central Nervous System (though there are some reports on cases where this does happen), a typical “hallmark” for what the biomedical field considers “cancer.”