In the investigation of superficial lymphadenopathy of unknown cause, fine needle aspiration (FNA) cytology plays an invaluable role. It enables the differentiation of benign lymphadenopathy from lymphoid and non-lymphoid malignancies, obviating the need for open biopsy, and allowing the triage of patients. Cytopathologists should be familiar with the typical FNA patterns of benign lymphadenopathy, and recognize and differentiate among categories. In a minority of cases of benign lymphadenopathy, FNA can render a specific diagnosis. Benign lymphadenopathies are generally categorized into reactive lymphoid hyperplasia (RLH), inflammatory or infectious processes, and benign lymphoproliferative disorders. RLH characteristically presents with a heterogeneous and polymorphous smear composed of normal cellular constituents of lymph nodes, in contrast with the homogeneous or monomorphic smear of most lymphomas. The caveat is that various malignant disorders may also present with polymorphous populations. It is also important to recognize thatbenign lymphoid smears may sometimes contain atypical cells that raise the suspicion of malignancy. Clinical information should always be the integral part of the diagnostic criteria in FNA of lymphadenopathy. If there is any doubt about the benign nature of the smear, it is prudent to suggest biopsy and ancillary studies.
Biopsy ; Biopsy, Fine-Needle* ; Diagnosis ; Diagnosis, Differential* ; Humans ; Lymph Nodes ; Lymphatic Diseases* ; Lymphoma ; Lymphoproliferative Disorders ; Pseudolymphoma ; Triage