[Histonet] IHC controls for Cytology

Dawson, Glen GDawson <@t> dynacaremilwaukee.com
Wed Dec 14 12:25:59 CST 2005

FFPE tissue sections are not appropriate controls for smears.  Kemlo is
correct, the control tissue/slide must be processed/stained exactly like the
test slide in order for it to be valid.  I do IHC on smears/PAPs
occasionally when absolutely nothing else is available, but I am sure to
tell the ordering pathologist that I do not have an appropriate control to

I routinely do a rapid melanoma procedure on smears so I have a bank of
known positive melanoma smears in my freezer, but that is the only one.  

It is unrealistic to believe that an IHC lab could have appropriate controls
for any situaion that may come up, but I can also see how a pathologist
needs to use whatever is available in an emergency situation.  I believe
that many of them will gleen what they can from these smears but not put
them in their report since an appropriate control is not available.  Then,
as with so many other situations, the IHC lab takes one for the team when it
comes time to bill.

Interesting thread,

Glen Dawson
IHC Manager
Milwaukee, WI

-----Original Message-----
From: Rogerson Kemlo (ELHT) Pathology
[mailto:Kemlo.Rogerson <@t> elht.nhs.uk]
Sent: Wednesday, December 14, 2005 9:14 AM
To: Orr, Rebecca; histonet <@t> lists.utsouthwestern.edu
Subject: RE: [Histonet] IHC controls for Cytology

Aren't controls supposed to be treated exactly the same as the test? So
unless you treat them exactly the same you will never know if you have a
false negative and I'm not bright enough to know if you could have false
positives too.

Hi everyone,

We have very recently begun to destain pap stained smears as  well as
unstained  cytology smears,  and run IHC.

Because my Docs are happy with the results, I anticipate receiving more
of these types of smears to run.

I only  have FFPE tissue in stock to use as control, so I give them the
slides with the disclaimer that the control has been treated differently
than the smear.

This seems to be acceptable as long as they can detect some positive
stained cells (TTF, PanCk, WT-1  Mart-1 for example). But if the smear
is negative, how can I be sure it's a true negative?  My antibodies
aren't really titered for  smears....

I would appreciate some comments from anyone who is running a
standardized protocol for smears. Do you have a set of smears you can
use as controls?  I have access to our molecular lab and there is
potential to make my own cell cultured controls,  what do you think?


Many thanks,



Becky Orr CLA,HT(ASCP)

IHC Lead 

Evanston Northwestern Healthcare



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