T-and NK-lymphoblastic lymphomas can co-express CD79a,take a look at:

Pilozzi E, Pulford K, Jones M, Muller-Hermelink HK, Falini B, Ralfkiaer E,
Pileri S, Pezzella F, De Wolf-Peeters C, Arber D, Stein H, Mason D, Gatter
K. 
Co-expression of CD79a (JCB117) and CD3 by lymphoblastic lymphoma.
J Pathol. 1998 Oct;186(2):140-3.

and

Gloeckner-Hofmann K, Ottesen K, Schmidt S, Nizze H, Feller AC, Merz H.
T-cell/natural killer cell lymphoblastic lymphoma with an unusual
coexpression of B-cell antigens.
Ann Hematol. 2000 Nov;79(11):635-9.

Dr. Alexander Nader
Path. Institut Hanuschkrankenhaus
Heinrich-Collin Straße 30
A-1140 Wien, Österreich
+43-1-910 21 DW:2422
 
Alexander.Nader@wgkk.sozvers.at <mailto:Alexander.Nader@wgkk.sozvers.at>

Alexander.Nader@univie.ac.at <mailto:Alexander.Nader@univie.ac.at> 

> -----Original Message-----
> From: Barry Madigan [mailto:madbaza@powerup.com.au]
> Sent: Friday, February 02, 2001 11:17 AM
> To: Histonet
> Subject: Lymphoma
> 
> 
> Hello Fellow Histo Netters
> 
> Has anyone come across a lymphoma that is CD20 negative but 
> both CD79a and
> CD45RO positive.
> All tonsil controls are ok and staining was repeated twice on 
> different days
> with the same results.
> Staining performed on other cases on these days was ok.
> 
> Regards
> Barry Madigan
> QHPSS
> Royal Brisbane Hospital
> Australia
> madbaza@powerup.com.au
> 
> 
>