Chin Med J (Taipei) 1998;61:S117.

Molecular Diagnosis and Biological Behavior of MALT Lymphomas

Kokichi Kikuchi, Shinichiro Kon

Department of Pathology, Sapporo Medical University School of Medicine

Abstract

Molecular approaches have been used for diagnosis and classification of lymphoproliferative diseases. Among those techniques, analysis of rearrangements of immunoglobulin (Ig) gene and T cell receptor (TCR) gene were most useful to confirm the clonality of lymphocytes. They were utilized not only in nodal lymphoproliferatve disorders, but also in extranodal ones.

The extranodal lymphoproliferative disorders, especially those originated from MALT (mucosa-associated lymphoid tissue), are considered to include low grade B cell malignancies. It is generally accepted that the most cases of reactive lymphoid hyperplasia (RLH) and pseudolymphomas in mucosal area are B cell malignant lymphomas. since the majority of the cases shows monoclonality of the Ig gene rearrangement. Gastric MALT lymphomas has been proved to relate closely with Helicobacter pylori (HP), and it has been reported they regressed after elimination of the HP. Their Ig molecules are considered to recognize autoantigens. However, no evident relationship has been reported between other MALT type lymphomas and certain exogenous antigenic factors.

We analyzed Ig gene rearrangement and gene segment usage of ocular adnexal lymphoproliferative disorders. This was extremely useful for the definite diagnosis of malignancy of the tumor. We found biased usage of D segment among ocular adnexal lymphomas. These molecular characteristics may suggest that the development of the lymphoma caused by some antigenic stimulation and may correlate with clinical course. Further, we analyzed the somatic mutations occurring in VH gene segments in a case of gastrointestinal lymphoma representing multiple polypoid lesions from the esophgus to the rectum. Genotypic study revealed the monoclonality in CDR3 area of each biopy specimens. Several somatic mutations were observed in Ig VH region sequences, suggesting correlation with biological behavior of this lymphoma.

[Chin Med J (Taipei) 1998;61:S117.]