Hi -

Different type of GI processing question. Big pieces,
not the biopsies.

Background history:
The students and I have always had to use one of the
processors in the histology lab to process their tissue
for their HT/HTL exams. We could only use one of the
four machines, and we had to use the processing
schedules already set up on the machines - we
couldn't change any schedule. We had to use the
schedules set up for histology - little biopsy schedule,
large pieces of tissue schedule, autopsy schedule,
stat kidney schedule, etc.

The best of the schedules for the students' type and
size of tissue used the following all with vacuum and 
40 degree C. heat, one hour at each station:
3 - alcoholic formalin
1 - 95% ethanol
3 - 100% ethanol
3 - xylene
4 - paraffin (60 degrees C.)

The usual tissue cut OK. Liver, kidney, lung.
Spleen was a little dry.

The hard tissues were almost impossible to
section (cervix, uterus, thyroid). They were 
too hard.

At the same time, any GI tissue (NOT biopsies,
but tissues 2-3 mm thick, about 2.5 cm long)
(stomach, large/small intestine, even appendix)
had micro-chatter in the epithelium, and the
connective tissue layer of the submucosa 
(between the muscularis mucosa and the
muscularis externa) would shred during sectioning.
I couldn't tell if it was over processed, since
placing an ice cube against the block to add
moisture to the epithelium resulted in the connective
tissue layer becoming whiter (which hinted to me
that this layer might be underprocessed.)

Anyway, histology got a new tissue processor,
and the School inherited the old one.

Since the tissues had been fixed for 4 weeks
in formalin (this is the tissue from surgery that
we are going to be dumping), I dropped the
formalin step, and added a 70% alcohol. I 
eliminated the heat at all stations, except
paraffin. I also eliminated the vacuum at all
stations except paraffin. I reduced the times to 
45 minutes in each station. The following is the
new schedule:

1 - 70% alcohol
1 - 95% alcohol
3 - 100% alcohol
3 - xylene
4 - paraffin

The hard tissues (uterus, cervix, thyroid) are cutting
like butter! They are wonderful!

Haven't tried a spleen yet.

However, the GI tissues are still shredding in the
connective tissue layer, and turning white with the
ice cube.

So - question time:

- What is so different about the connective tissue
layer in the GI? Amount of bound/unbound water?

- What direction should I go now?
Increase or decrease time/heat/vacuum? 

- Is the sequence/series of solutions OK?
I'm thinking about adding another 95% alcohol, but 
don't think that is going to make much difference 
with the connective tissue layer.

Thanks for any and all suggestions.

Peggy A. Wenk, HTL(ASCP)
William Beaumont Hospital
Royal Oak, MI 48073