Diagnosis of peripheral T-cell lymphoma by fine-needle aspiration biopsy: a cytomorphologic and immunophenotypic approach.

The diagnosis of T-cell lymphomas by fine-needle aspiration biopsies (FNAB) is extremely difficult. This is mainly due to the rarity of the disease, the morphologic similarity to reactive lymphadenopathy, and the difficulty in identifying abnormal T-cell antigen expression. We studied FNAB of histologically proven T-cell lymphomas in an attempt to identify the salient cytomorphologic features as well as the surface marker attributes of the disease. Twenty cases were reviewed. The smears were evaluated for overall cytologic pattern and percentage of abnormal cells. A critical review of flow cytometric (FCM) antigen expression of the lymphomas was also performed. There were 6 female and 14 male patients, with an age range of 9-84 yr (median, 36 yr). Fourteen cases (70%) showed polymorphous smears, and 6 cases (30%) showed monomorphous smears. Abnormal cells ranged from 10-100% (median, 60%). Abnormal T-cell antigen expression by FCM analysis was seen in 17 cases (85%). The most common aberrant T-cell antigen pattern was loss of 3 or more pan-T-cell antigens (n = 10). The most common individual T-cell antigen loss was that of CD7 (n = 10), followed by loss of CD5 (n = 5). There was also loss of CD4 and CD8 (n = 5), loss of CD5 and CD7 (n = 5), complete loss of CD3 (n = 4), coexpression of CD4 and CD8 (n = 1), and partial loss of CD3 (n = 1). CD56 was expressed in 2 cases. CD1a was tested in one case and was positive. CD4/CD8 ratio was elevated (>2.5) in 9 cases (53%), with a range of 3/1-57/1 (median, 12/1). TCR gene rearrangement using PCR was positive in 7 of 9 tested cases. Our findings suggest that the diagnosis of peripheral T-cell lymphomas can be achieved by FNAB in the majority of cases through close analysis of the morphology. This can be supported by a critical analysis of the phenotype using two or three-color flow cytometry with an attempt at identification of one or more abnormal T-cell antigen expression and/or loss. This can be supplemented by CD4/CD8 ratios and T-cell receptor gene rearrangement analysis. Copyright 2000 Wiley-Liss, Inc.