Peripheral T/NK-cell lymphoma: a report of the IXth Workshop of the European Association for Haematopathology.
OBJECTIVE
In April 1998, The European Association for Haematopathology organized the IXth workshop on peripheral T-cell and NK-cell lymphomas and leukaemias. The workshop focused on unusual subtypes of these rare malignancies, allowing evaluation of the recently published WHO classification of neoplastic diseases of the lymphoid tissues.


RESULTS
One-hundred and three cases were centrally immunophenotyped and hybridized for EBER1/2 of Epstein--Barr virus. All cases were reviewed by a panel of experienced haematopathologists and classified according to the new WHO classification for lymphoid neoplasms. Three cases were considered as precursor T-cell and 95 cases as peripheral T/NK-cell lymphoma/leukaemia. Although the cases represented a selected series of unusual cases, the following conclusions could be made: (i) Most lymphomas except the hepatosplenic gamma/delta T-cell lymphomas showed a rather broad morphological spectrum, with differences both between and within individual tumours. (ii) This heterogeneity was also reflected by the immunophenotype, for instance a variable expression of CD30 was found in many enteropathy type T-cell lymphomas. (iii) Exceptions in phenotype were regularly found in almost all categories, indicating that phenotype should not be the final determining factor in classification. (iv) The great majority of T-cell lymphomas expressed the alpha/beta T-cell receptor, with the exception of all but one hepatosplenic T-cell lymphomas and a few other extranodal peripheral T cell lymphomas. (v) Malignancies of precursor cells, blastic NK-cell lymphoma/leukaemia, adult T-cell lymphoma/leukaemia and most AIL-type T-cell lymphomas did not express cytotoxic molecules such as TIA1 and granzyme-B. In contrast, all five aggressive NK/T-cell lymphomas/leukaemias, a single case of large granular lymphocyte leukaemia and 40 of 47 primary extranodal lymphoma/leukaemias expressed these molecules. In hepatosplenic gamma/delta T-cell lymphoma, five of six cases showed expression of TIA1 but not of granzyme-B. (vi) Seven tumours developed after organ-transplant, four cases being EBV-positive. No distinct phenotype could be attributed to these cases.


CONCLUSIONS
Most peripheral T/NK cell lymphomas could be categorized as distinct entities as described in the recently proposed WHO classification for lymphoid neoplasms.
Department of Pathology, Leiden University Medical Center, Leiden, The Netherlands. p.m.kluin@path.azg.nl
P M
PM
Kluin
A
A
Feller
P
P
Gaulard
E S
ES
Jaffe
C J
CJ
Meijer
H K
HK
Müller-Hermelink
S
S
Pileri
D000328:Adult; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007119:Immunoblastic Lymphadenopathy / Q000235:genetics / Q000276:immunology / Q000473:pathology; D007120:Immunochemistry; D016130:Immunophenotyping; D007414:Intestinal Neoplasms / Q000235:genetics / Q000276:immunology / Q000473:pathology; D007694:Killer Cells, Natural / Q000276:immunology; D016403:Lymphoma, Large B-Cell, Diffuse / Q000235:genetics / Q000276:immunology / Q000473:pathology; D008228:Lymphoma, Non-Hodgkin / Q000145:classification* / Q000235:genetics / Q000276:immunology / Q000473:pathology; D008297:Male; D008875:Middle Aged; D012367:RNA, Viral / Q000235:genetics; D012878:Skin Neoplasms / Q000235:genetics / Q000276:immunology / Q000473:pathology; D013601:T-Lymphocytes / Q000276:immunology
C099537:Epstein-Barr virus encoded RNA 1; C106732:Epstein-Barr virus encoded RNA 2; D012367:RNA, Viral