BACKGROUND.
Low-grade lymphomas can be difficult to diagnose in cytology specimens, especially marginal zone B-cell lymphomas (MZLs). MZL is a low-grade lymphoma characterized by a heterogeneous lymphoid population, which can be difficult to distinguish from reactive processes in cytology specimens.
METHODS.
Fourteen cytology specimens of MZL from 11 patients with histologically confirmed MZL (n Ο 10) or flow cytometry (FC)-confirmed MZL (n Ο 1) were reviewed, including 13 fine-needle aspiration biopsy (FNAB) specimens (salivary gland, n Ο 6; lung, n Ο 3; lymph node, n Ο 2; breast, n Ο 1; and soft tissue, n Ο 1) and 1 pleural effusion specimen. Cytologic preparations included air-dried and alcohol-fixed direct smears, ThinPrep slides, and cell blocks. FC studies were available in six specimens.
RESULTS. All
13 FNAB specimens were composed predominantly of intermediatesized lymphoid cells with interspersed small, round lymphocytes and transformed cells. The intermediate-sized cells displayed a moderate amount of cytoplasm, slight nuclear membrane irregularities, and inconspicuous-to-absent nucleoli. The pleural fluid contained mostly small-to-intermediate-sized, round lymphocytes. In 10 specimens, the intermediate-sized cells often showed plasmacytoid morphology, which were seen best in Diff-Quik (Mercedes Scientific Co., Inc., Sarasota, FL)-stained slides. Monocytoid cells (n Ο 6 specimens), plasma cells (n Ο 7), lymphohistiocytic aggregates (n Ο 11), and tingible body macrophages (n Ο 5) were variably identified. Lymphoepithelial lesions were not observed. Three specimens with FC studies showed a phenotype compatible with MZL, and three specimens were nondiagnostic. CONCLUSIONS. Cytologic features suggestive of MZL included abundant intermediate-sized lymphoid cells with mild atypia in a background of small lymphocytes and transformed cells, often with plasmacytoid morphology. Flow cytometry was beneficial only in selected MZL cytology specimens. Surgical correlation may be necessary to confirm the diagnosis. Cancer (Cancer Cytopathol) 2003;99:301-9.