Fine-Needle Aspiration Biopsy Diagnosis of T-Cell Non-Hodgkin Lymphomas: Morphologic Features, Ancillary Testing, and Diagnostic Pitfalls

FNAB, when appropriately triaged for preparation of a cell block, immunocytochemistry, flow cytometry, and molecular studies can provide a definitive or near-definitive diagnosis in some T-cell lymphomas (e.g., T-LBL, systemic ALCL, BIA-ALCL effusions), whereas in other entities it serves mainly to raise strong suspicion and guide tissue biopsy (e.g., nTFHL-AI, PTCL-NOS). Understanding which entities can be reliably recognized by cytologic assessment, which ancillary panels are most informative, and where the limits of cytopathology lie are essential for optimal patient management and for appropriate use of the WHO Reporting System in daily practice.