Pineal Region Tumors
As mentioned in the PRIMER, the pineal gland hangs on the brain behind
its very center. French 18th century scientist Rene Descartes thought that
the pineal gland was the core of the soul, noting that it was the only
unpaired organ in the body, and located in the center of the brain. He
thought that the gland controlled the movement of the various body "humors."
In fact, the pineal gland is the "third eye" of the brain, and is responsible
for telling the brain when it is day or night. It also controls the body's
hormonal systems, sleep-wake cycle, and other so-called "circadian" body
rhythms. It is in essence, the body's internal clock."
The gland produces a hormone called melatonin, (now a popular over-the-counter
seller). Melatonin levels are what directly influence the function of various
brain centers (appetite, sleep, the hypothalamus and pituitary gland).
The cells of the pineal gland are unique in that they are not related to
either the support cells of the brain (i.e. astrocytes, etc.), nor to the
brain neurons. Rather, they develop on their own. For this reason, true
pineal cell tumors are quite different from other brain tumors.
The pineal gland is also filled with brain support cells (astrocytes)
and has a very dense input of nerve fibres coming from the eyes via a very
circuitous and complicated route. Thus, the tumors of the astrocyte support
cells of the pineal region are the same as the astrocytomas and GBM.
Pineal tumors, themselves, vary. They include:
-
Pinealocytoma ("benign" pineal cell tumor)
-
Pineoblastoma (more aggressive pineal cell tumor)
-
Pineal germinoma ( aggressive primitive cell tumor growing in the pineal
region)
-
Pineal teratomas (rare tumors of multiple cell types that grow in the pineal
region)
-
Pineal Cysts (most often not treated, unless large enough to cause hydrocephalus
or visual symptoms)
Making the Diagnosis
A combination of CAT scan, MRI, and spinal fluid studies (including
"markers" such as AFP, and spinal fluid cytology), will aid the surgeon
to deliver a very good guess or outright diagnosis.
Treatment Decisions -- Tumor Biopsy
With all of these possibilities in such a small area, it is no wonder
that most physicians feel strongly that at least a biopsy should be taken
prior to considering a treatment course.
-
Surgical Removal. These tumors should be approached surgically at first,
with a best effort approach to remove as much as, if not all, of the tumor.
With current surgical technology, the down side has essentially been reduced
to well below the 2% risk mark, making the decision to operate much less
difficult than previously. Today, the surgery can be minimized so that
recovery time is shortened. Some patients with larger tumors may also develop
hydrocephalus, requiring the placement of a shunt at the time of surgery
or thereafter.
-
Radiation. Some centers perform radiation, at least in a "test" dose (in
the case of the germinoma) since some of the primitive tumors are quite
sensitive, a full course of radiation might be considered.
-
Craniospinal axis. If the spinal fluid cytology is positive, so-called
"craniospinal" axis therapy may be considered. This is done because some
of these tumors will "seed" down from the brain into the spinal canal.
-
Chemotherapy. Many chemotherapy choices may be available. Some of these
tumors are quite sensitive to chemotherapy, accounting for the vigorous
chemo-approach of many neurooncologists to such lesions.
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