Box 1 • Distinction between SMZL, SDRPL, and SBLPN/HCLv requires integration of clinical features, immunophenotype, and morphology in blood, bone marrow, and spleen. Next generation sequencing can be of added value. If the spleen is not available for evaluation, distinction may not be possible. • TFH cells can be increased in all MZLs, which should be distinguished from T-cell lymphoma by performing appropriate immunohistochemical and molecular studies. • Strict criteria for transformation in MZL are lacking and borderline cases suspicious for transformation do occur. Risk of transformation may be associated with genetic abnormalities (NOTCH3 mutations, complex karyotype). • PNMZL is not limited to the pediatric age group and can occur in young adults. • PNMZL might have overlapping features with PTFL but the possible relationship remains to be determined. • B-cell clonality detection is vital to differentiate PNMZL from reactive conditions such as atypical marginal zone hyperplasia.