Saturday, June 19, 2010

Big words in Grade IV

We've had several people ask what is meant by "grade IV" tumour - and several who thought grade 4 and stage 4 are the same thing. Here is my attempt to explain it all a bit better.

No tumour in the brain is considered benign, since any brain tumour can cause serious problems. As a result, rather than classifying tumours as malignant or benign, brain tumours are classified by grade. A Grade I brain tumour would be considered benign if it were found in any other part of the body. It is not cancerous. Grade II is a slow-growing slightly malignant tumour. A grade IV tumour is a highly malignant, fast-growing brain tumour.

Kol's tumour is a Grade IV. It is considered a primary brain tumour - which means that it started in the brain. It is also a primitive neuroectodermal tumor (PNET), so named because of the type of cell they believe it originated from. Most PNET tumours are medulloblastomas, and are intratentorial (iPNET) - meaning they are in the lower part of the brain - kind of behind the ears. Kol's is a neuroblastoma subtype rather than the medulloblastoma, and it is supratentorial (sPNET) - which means that it is in the top part of the brain - above the ears.

Are you still following?

We were told before Kol's surgery that most tumours where Kol's is are low grade - meaning either a grade I or II. I found on one website (don't know how trustworthy or up to date it is) that the ratio of PNET medulloblastomas to PNET nueroblastomas is 25:1, and the incidence of a medulloblastoma is 1 in 200 000. If my math is right, that makes a neuroblastoma 1 in 5 000 000. The position of it (supratentorial) may make it even more rare.

Primary brain tumors are not classified into stages like most other cancers are. This is because the size of a brain tumor is less important than its location and the type of brain cell that it comes from.

Any questions - either for us, or ones that we could ask the oncologists? We already have some questions we'd like to ask, but we also know that everyone thinks differently, and we'd like to get as complete info as possible at our meeting on Monday. Post them in the comments, or if you'd rather, you can e-mail them to me. My address is


  1. Thanks Kristen, this is a great explanation.

  2. Great explanation. So much to learn and absorb. I am glad you have a meeting today to get some answers, and possible plan. Waiting is never fun.