Aberrant expression in lymphoma, a diagnostic pitfall.

One of the major difficulties in practical hematopathology is to accurately assign cell lineage and thus ensure proper classification of lymphomas. The lineage-specific markers of lymphoma are detected by immunohistochemistry or flow cytometry immunophenotypic methods. However, aberrant gain or loss of these markers is occasionally encountered during daily practice, which often creates diagnostic challenges. In addition, lymphoma may aberrantly express non-hematopoietic markers, and vice versa. This review article provides an overview of aberrant gain of expression of lineage-associated antigens in mature lymphoid neoplasms, including recommendations to avoid diagnostic pitfalls and ultimately to reach accurate diagnoses.