Cytopathologic Diagnosis of Small B-Cell Lymphomas

BACKGROUND: Cytologic examination of lymph nodes and serous effusions is of value in the diagnosis of small cell lymphomas. The World Health Organisation (WHO) has recently published a reporting system relating to the cytologic examination of lymph nodes, spleen, and thymus to standardise the approach to reporting such specimens. SUMMARY: An overview of the WHO reporting system is given with particular reference to the diagnosis of small B-cell lymphomas. The role of rapid on-site evaluation and ancillary testing is discussed. The cytomorphological features of specific small B-cell lymphomas and associated ancillary testing are described. KEY MESSAGES: The WHO reporting system provides a standardised approach to the reporting of cytological specimens from lymph nodes, the spleen, and the thymus. Small B-cell lymphomas pose a challenge to the cytopathologist due to their morphologic overlap with each other and reactive conditions. The importance of correlation and integration of cytomorphological appearances with clinical features and ancillary testing modalities to obtain a final diagnosis is emphasised. The present review includes a description of cytomorphological features according to pattern recognition and provides an overview of diagnostic criteria for specific entities based on cytomorphology alone and in combination with ancillary tests in different clinical settings discussing differential diagnoses and potential pitfalls.