Re: sentinel node evaluation
The topic of sentinel nodes has been on this list repeatedly, and a good
thing it is. Many of us are making very heavy weather of this problem. In
fact, "sentinel node" bids fair to become the second dirtiest word in
surgical pathology - I've already told you what the first one is.
First of all, for those of you out in otolith land, the clinical basics: Many
cancers spread first to nearby regional lymph nodes. Breast cancers spread
first to axillary nodes, and melanomas of the extremities usually to the
nodes that drain the extremities. Cancer spreads first to the node in front -
the "sentinel node" and only later to the nodes above it. If the sentinel
node doesn't contain cancer, then you don't have to subject the patient to a
much larger operation to get the rest of them out. - But how do you find the
sentinel node, and how do you tell if it's got cancer in it or not?
If you inject dye around the tumor, you can watch the dye go up the lymphatic
channels into the lymph node. A triarylmethyl dye called isosulfan blue
(Lymphazurin 1%, United States Surgical Corporation) - akin to Patent Blue V,
I believe - serves pretty well, and they use it. More elegant is sulfur
colloid labeled with technetium 99m (a gamma emitter with a half life of 6
hours). Most centers use both agents.
The radioactivity is thus the first consideration. The amount of radioisotope
is so small that it can be ignored in grossing the specimen - in fact you
could EAT the specimen and it wouldn't harm you. That's the practical answer,
but the radiophobes are eager to create rituals - such as locking the poor
lymph node up in a refrigerator for three days - to keep the radiobureaucrats
employed. Many larger facilities have dispensed with these rituals, and it's
worthwhile to call your nearby large facilities for advice.
It's quite controversial whether any studies on the excised lymph node are
more useful than H & E in finding cancer. Many large centers do only an H &
E, but there's great pressure to use keratin or melanoma immune stains. The l
ittle hospitals I work in don't do immune stains, and in that circumstance
one hopes to resist the pressure to get them done.
Frozen section on sentinel nodes seems generally considered inadvisable, but
some surgeons want touch or scrape preparations.
I've been reviewing this topic this week, since one of my hospitals with an
elderly (he's only 9 years younger than ME) solo pathologist is setting the
procedure up and is making rather heavy weather of it - even the most godlike
of surgeons learns the procedure remarkably slowly. I'll keep people informed
of what I find out if you're interested.
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