Touch Smear Cytology in Epstein-Barr Virus-Positive Nodal T- and NK-Cell Lymphoma: Cytological Features of This Rare, Aggressive Lymphoma.

Epstein-Barr virus (EBV)-positive nodal T- and natural killer (NK)-cell lymphoma (EBV+ NTNKL) is a recently characterised rare malignancy arising from cytotoxic T or NK cells, typically presenting as nodal disease in adults. This lymphoma was recently recognised in the 5th edition of the World Health Organization Classification of Haematolymphoid Tumours. A comprehensive review of the existing literature revealed no cytological descriptions of this disease. Here, we present the first description of cytological observations from a touch smear of EBV+ NTNKL. In this case, the cytological features of EBV+ NTNKL included centroblastoid nuclei, resembling diffuse large B-cell lymphoma (DLBCL), along with abundant cytoplasm containing azurophilic granules observable with May-Giemsa staining. These cytoplasmic features are consistent with the cytotoxic T/NK-cell lineage of the tumour cells. In the cytological diagnosis of EBV+ NTNKL, it is critically important to understand the distinguishing features that differentiate it from morphologically similar DLBCL. It is also necessary to differentiate EBV+ NTNKL from extranodal NK/T-cell lymphoma, which is an important differential diagnosis in the evaluation of EBV-associated lymphomas. Recognition of the specific cytomorphological features of this lymphoma is of practical significance when fine-needle aspiration cytology, frequently used as an initial diagnostic step for lymph node lesions, is employed and when touch smear cytology is performed to complement histological findings.