Marginal zone and mantle cell lymphomas: assessment of cytomorphology in subtyping small B-cell lymphomas.

The diagnosis of malignant lymphomas by fine-needle aspiration biopsy (FNAB) is increasing in utilization. The cytomorphologic distinction among the small B-cell lymphomas may be quite difficult. We are unaware of anyone who has compared directly mantle cell lymphoma (MCL) and marginal zone lymphoma (MZL) in FNAB. Our major goal was to examine the cytomorphologic attributes of MCL and MZL and to look for features distinctive of or suggestive of either neoplasm. Seven immunophenotypic MCL and seven immunophenotypic MZL aspirates were evaluated for a number of cytomorphologic features in direct smears. Features favoring MCL include a relatively monomorphic cellular population, prominent nuclear membrane contour irregularities, and mitotic figures. Conversely, a polymorphic cellular population suggested MZL. However, due to extensive overlap of specific cytologic features, the two lymphomas cannot be definitively distinguished based solely on cytomorphology. Although there are cytomorphologic attributes suggestive of either MCL or MZL, considerable overlap exists. Based on an individual case basis, the distinction cannot be made reliably by morphology alone; ancillary studies, e.g., immunophenotyping, are essential.