Hi,
Before answering your questions, I would just like to give a brief background about the classification of
brain tumors. Brain tumors are classified as primary if they originated from the brain itself, and secondary
(or metastatic) if they came from some other organ (e.g. lungs, breast, kidneys, skin). Secondary brain
cancers are by definition, malignant, since these are actually metastatic from a site outside the brain. Most
of the primary brain tumors originate from glial cells. These are the cells which provide nutrition and other
forms of support to the nerve cells in the brain. There are many types of glial cells (example: astrocytes,
ependymal cells, oligodendrocytes, etc.) and the primary brain tumor is named after which glial cell it was
derived from (e.g. astrocytoma, ependymoma, oligodendroglioma, etc).
The term”benign”, when applied to primary brain tumors, may be a misnomer. Slow-growing or low-grade gliomas
are considered as benign, but some of these tumors – low grade astrocytomas in particular – can infiltrate
surrounding normal tissue and can later progress into frankly malignant types. I would prefer to think of the
“benign” or “malignant” types of primary brain tumors not as distinct entities but as a spectrum of
malignancy, with “benign” lesions which rarely metastasize on one end and the aggressive high grade
malignancies on the other end. Bearing this in mind, it is not surprising to see “benign” brain tumors get a
type of treatment which is more extensive (e.g. radiation involving the “entire spine”) and is seemingly more
appropriate for “malignant” types.
Tumors (whether benign or malignant) develop as a result of certain mutations in the genes of cells which
regulate the cell’s life span and ability to multiply. Typically, the mutations occur only in a very small
number of cells (sometimes, just one or two cells get mutations). Because of the mutation, this small focus
of cells begin to multiply faster than usual, eventually resulting in a tumor which is big enough to be
noticed by MRI or CT scan. With some tumors, however, the mutation does not happen to just a few cells, but
to the whole class of cells with a similar histologic type. Such a phenomenon can happen with glial cells in
the brain, resulting in multiple foci of brain tumor. This may explain the fact that your son had two benign
tumors occurring at the same time.
Technically speaking, benign tumors do not have the ability to “seed” or metastasize. The ability to “break
off and spread” to distant areas is what differentiates malignant from benign lesions.
I hope the explanation helps.
