MARGINAL ZONE B-CELL LYMPHOMA WITH MONOCYTOID B-CELL LYMPHOCYTES IN PEDIATRIC-PATIENTS WITHOUT IMMUNODEFICIENCY - A REPORT OF 2 CASES

We report two cases of marginal zone B-cell lymphoma in two patients 6 and 18 years of age, respectively (cases 1 and 2) who had no clinical evidence of immunodeficiency or risk factors for human immunodeficien cy virus (HIV) infection. Histologic analysis in both cases revealed d iffuse nodal effacement by a monotonous population of atypical lymphoi d cells with abundant pale cytoplasm and round to oval nuclei, with ve ry infrequent mitotic activity. The neoplastic cells in both cases wer e of B-cell Lineage (CD20 and CD79a positive), with CD43 coexpression. One case showed monoclonal light chain expression, and polymerase cha in reaction analysis demonstrated clonal rearrangements of the immunog lobulin heavy chain gene in both eases. Abnormal cytogenetic findings were detected in case 2, in which metaphase spreads revealed trisomy 1 3 (karyotype 47, XY,+13). Although trisomy 13 has been described in as sociation with acute nonlymphocytic leukemias and myelodysplastic synd romes, this case represents the first documented association of trisom y 13 with marginal zone B-cell lymphoma. Interphase cytogenetics analy sis for trisomy 3, reported to be associated with mucosa-associated ly mphoid tissue (MALT) lymphomas, was negative in both cases. Although l ow-grade lymphomas of the MALT type have been reported in HIV-positive patients, the two cases reported here are unique in that they occurre d in young patients without HIV infection or any other evidence of imm unodeficiency.