Follicular and Marginal Zone Lesions of the Lymph Node

Abstract

We discuss a case of atypical localized follicular and marginal zone B-cell hyperplasia with immunoglobulin kappa light chain restriction that presented as a localized proliferation in an inguinal lymph node of a 33-year-old woman. No clonal proliferation could be detected using CDR3- and CDR2-related primer pairs of immunoglobulin heavy chain genes. No break events or translocation could be detected for all typical known genes involved in follicular neoplasia (BCL-6 immunoglobulin heavy chain and BCL-2). After reviewing all the differential diagnoses of described subtypes and variants of follicular lymphoma and marginal zone B-cell lymphoma, we finally interpreted this case as a localized pseudotumor mimicking the whole range of B-cell activation and differentiation similar to hyperimmune B-cell reactions. No causative agent was found, nor was one detected, by clinical investigations. Although we could exclude all known types of follicular neoplasia, in view that the sensitivity and specificity of molecular detection of clonality was not 100%, a neoplastic process involving the whole range of follicular and postfollicular differentiation in B cells could not be firmly excluded. Therefore, close follow-up or local radiotherapy must be considered as therapeutic options, similar to comparable processes of undefined significance in other localizations, eg, monoclonal gammopathy of unknown significance or extranodal marginal zone B-cell lymphoma of the skin. The latter has even been designated by some Dutch dermatopathologists “pseudo-pseudo lymphomas” (van Unnick, personal communication).