Rarity of genomic instability in pathogenesis of systemic anaplastic largecell lymphoma (ALCL) in immunocompetent patients

Microsatellite instability (MSI) is a recently described type of genetic al teration resulting from defects in the DNA mismatch repair genes that appea rs to play an integral role in neoplastic transformation. MSI has been desc ribed in a wide variety of malignancies; however, data regarding the role o f;MSI in the pathogenesis of non-Hodgkin's lymphoma (NHL) are limited. MSI appears to be important in some T-cell lymphomas, including ALCL arising in immunocompromised patients. In addition, MSI has recently been identified in CD30(+) cutaneous lymphoproliferative processes and lymphoblastic lympho ma. In this study, we have analyzed five well-characterized cases of system ic T-cell ALCL arising in immunocompetent patients for the presence of MSI. Genomic DNA isolated from paired normal and tamer tissue was analyzed at s even microsatellite loci by polymerase chain reaction. We were unable to id entify MSI or loss of heterozygosity (LOH) in our cases, suggesting that ab normalities in the DNA mismatch repair system do not play a major role in t he pathogenesis of most systemic ALCL. Our data provide additional molecula r evidence that the various subgroups of lymphoma with ALCL morphology are biologically distinct processes. HUM PATHOL 30:173-177. Copyright (C) 1999 by WB. Saunders Company.