We report a 54-year-old female patient with Waldenström macroglobulinemia who shows concomitant partial tetrasomy 3q in the form of an additional isochromosome 3q, and trisomy 18. To our knowledge, isochromosome 3q has not been reported in chronic lymphoproliferative disorders. A review of the literature on karyotypic aberrations in Waldenström macroglobulinemia suggests that additional copies of the long arm of chromosome 3 and chromosome 18 may play a possible role in the pathogenesis of a subset of this disorder.