[Histonet] Revealing lymph nodes

[RSRICHMOND <@t> aol.com]

Several correspondents report having trouble getting clearing fixatives to 
work. Let's look at methods.

(For people new to this issue - we're talking about fixation methods that 
render lymph nodes opaque while making the surrounding adipose tissue clear - for 
finding lymph nodes in cancer resection specimens.)

1. Overnight fixation is needed.
2. You need an adequate volume of fixative for the amount of tissue to be 
fixed, and that can be quite a lot.
3. Before you put the fatty mesenteries in the fixative, you have to slice 
them thin enough for the fixative to penetrate them. It's helpful to stir the 
container after an hour or so of fixation.
4. Looking for lymph nodes in the fixed tissue remains time-consuming, and it 
requires good ventilation.

I've successfully used Davidson's fixative (three parts water, three parts 
ethanol, two parts 37% formaldehyde [strong formalin, not buffered], and one 
part glacial acetic acid. Of commercial products I've had good results with one 
called O-Fix, not so good with at least one of the others.

In the immortal words of Herman Melville's Moby-Dick, chapter 95:

"mincing the horse-pieces of blubber for   the pots; an operation which is 
conducted at a curious wooden horse,   planted endwise against the bulwarks, and 
with a capacious tub beneath  it, into which the minced pieces drop.... Bible 
leaves! Bible leaves! This is the invariable cry from the mates to the 
mincer. It enjoins him to be careful, and cut his work into as thin slices as 
possible, inasmuch as by so doing the   business of boiling out the oil is much 
accelerated, and its quantity considerably increased, besides perhaps improving it 
in   quality."

Bob Richmond
Gastonia NC