Atypical marginal zone hyperplasia of tonsil with immunoglobulin light chain restriction Prabhjot Kaur, MD* and Norman B. Levy, MD This is a case of tonsillar enlargement in an immune compromised, 9-year-old child with aplastic anemia. The tonsil showed florid follicular and interfollicular hyperplasia (Image 1A). The expanded marginal zones contained a mixture of small centrocyte-like cells, monocytoid cells, and numerous transformed large lymphocytes (Image 1B). The CD20 positive B lymphocytes (Image 1C) were negative for epstein-barr virus (EBV). The germinal center lymphocytes were positive for CD10 (Image 1D) and negative for Bcl2 (Image 1E). Flow analysis detected a B-cell population with lambda Ig light chain restriction (Image 1F). Molecular stud- ies, however, showed a polyclonal B-cell population (Image 1G). Differential diagnosis included atypical marginal zone B-cell hyperplasia, marginal zone B-cell lymphoma, and im- munodeficiency-associated B-cell lymphoproliferative disor- der. Because of the absence of B-cell clonality by molecular analysis along with the absence of EBV infection by EBV- encoded RNA (EBER)-in situ hybridization studies, and a prior report by Attygalle et al. [1], the diagnosis of atypical marginal zone hyperplasia was rendered. In 2004, Attygalle et al. [1] reported a retrospective study which included six childhood cases, between the ages of 3 and 11, with tonsil- lar and appendiceal marginal zone proliferations displaying a naı ¨ve B-cell phenotype and lambda light chain restriction. All cases were found to be polyclonal by molecular analysis. No lymphoma-directed therapy was given to these children, and none of the children developed recurrent or new lesions after a follow-up of 3–13 years [2]. Similar cases have been described by Taddesse-Heath et al. [3]. Swerdlow reported a similar case in the adenoid of an 8-year-old girl but with mono- clonal heavy chain VJ gene rearrangements [4]. These mar- ginal cell proliferations are rare, and there is confusion on whether these are atypical hyperplasias or marginal zone lymphomas and if lymphomatous whether of mucosa associ- ated lymphoid tissue type (MALT lymphoma) or nodal type [3,5]. Marginal zone lymphoma of MALT lymphoma are extremely rare in native MALT sites of tonsil, adenoids, Peyer’s patches and appendix [6] especially in children [3,4,7] and occur usually outside of the native MALT sites, like the pa- rotid MALT lymphomas in human immunodeficiency virus patients and Helicobacter pylori infection-associated gastric MALT lymphomas, followed by orbital and skin sites [7]. Image 1. (A) Tonsil with follicular hyperplasia and expanded marginal zones (hematoxylin–eosin, original magnification: 203). (B) Marginal zones contain a mixture of small centrocyte-like cells, monocytoid cells and numerous transformed lymphocytes (original magnification: 4003). (C) CD20, also seen in intraepithelial B lymphocytes (original magnification: 203). (D) The germinal center lymphocytes are positive for CD10 (original magnification: 203). (E) The germinal center lymphocytes are negative for Bcl2 (original magnification: 203). (F) Flow analysis showing lambda Ig light chain restriction. (G) Molecular studies showing polyclonal B-cell IgH gene rearrange- ment. Conflict of interest: Nothing to report. *Correspondence to: Prabhjot Kaur, Department of Pathology, Dartmouth Hitchcock Medical Center, 1 Medical Center Dr., Lebanon, NH 03756. E-mail: prabhjot.kaur@hitchcock.org Department of Pathology, Dartmouth Hitchcock Medical Center, Lebanon, New Hampshire Received for publication 9 June 2011; Revised 30 June 2011; Accepted 6 July 2011 Am. J. Hematol. 87:424–425, 2012. Published online 14 July 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/ajh.22132 AJH Educational Material Images in Hematology V V C 2011 Wiley Periodicals, Inc. American Journal of Hematology 424 http://wileyonlinelibrary.com/cgi-bin/jhome/35105