Fine needle aspiration cytology of CD56-positive natural killer/T-cell lymphoma of soft tissue

BACKGROUND. Extranodal natural killer (NK)/T-cell lymphoma, nasal type, is a rare form of lymphoma with a predilection for Southeast Asians, including Koreans, and Central and South Americans. It has a high association with Epstein-Barr virus (EBV) and expression of CD56 antigen. In the current study, the authors reviewed the fine needle aspiration (FNA) cytology of NK/T-cell lymphoma involving soft tissue to identify characteristic cytologic features. METHODS. Ten FNAs of soft tissue involvement by histologically documented NK/T-cell lymphoma from eight patients (three nasal primary and five extranasal primary tumors) were included in the retrospective study of a six-year period (1996-2002). Diff-Quik- and Papanicolaou-stained smears were reviewed, as was the biopsy material, including immunohistochemical stains and in situ hybridization studies for EBV. Clinical information was obtained from the patients' medical records. RESULTS. Specimen sources were skin and subcutaneous tissue of the neck (3), arm (3), breast (2), and abdominal wall (1) and soft tissue of the buccal area (1). The smears were moderately to highly cellular in the extensively necrotic background, with an abundance of apoptotic debris. Single, scattered tumor cells had pleomorphic nuclei, coarse chromatin, indistinct or several small nucleoli, and eccentric bluish cytoplasm. Neutrophils were typically rare in most cases except in one case complicated by abscess. CONCLUSIONS. Fine needle aspiration can be a useful adjunct in the diagnosis of the nasal and extranasal NK/T-cell lymphoma. The presence of malignant lymphoid cells in a necrotic background with an abundance of apoptotic bodies is a highly characteristic and consistent finding in FNA of NK/T-cell lymphoma involving soft tissue.