Cytological analysis revealed large atypical lymphoid cells with irregular nuclei, prominent nucleoli and basophilic vacuolated cytoplasm ((a), May-Grünwald-Giemsa; (b), Papanicolaou). By immunohistochemistry of a corresponding cell block specimen, the large cells were strongly positive for CD45 (c), CD20 (d), and CD79a (e), and were negative for CD138 (f), indicative of a mature B-cell immunophenotype.