Programmed death‐1 expression in cutaneous B‐cell lymphoma

Background Numbers of programmed death‐1 ( PD ‐1) positive T cells have prognostic significance in some types of nodal B‐cell lymphomas, but data on PD ‐1 expression in cutaneous B‐cell lymphoma ( CBCL ) are few. In this study we determined the expression and distribution of PD ‐1 on neoplastic B cells and reactive T cells in skin sections from primary CBCLs . Methods By means of immunohistochemical staining, PD ‐1 expression was investigated in skin biopsies from 10 patients with primary cutaneous marginal zone lymphoma ( PCMZL ), 18 patients with primary cutaneous follicle center lymphoma ( PCFCL ) and 12 patients with primary cutaneous diffuse large B‐cell lymphoma–leg type ( PCDLBCL–LT ). Results Neoplastic B cells were negative for PD ‐1 in all cases, except for two cases of PCDLBCL–LT . The frequency of PD ‐1 + T cells was significantly higher in PCFCL than in PCMZL and PCDLBCL–LT , accounting for 20, 10 and 3% of the total number of infiltrating cells, and 60, 20 and 15% of the total number of CD3 + T cells, respectively. Conclusions PD ‐1 is rarely expressed by the neoplastic B cells in CBCL . High percentages of PD ‐1 + T cells, particularly if found outside germinal centers, support a diagnosis of PCFCL .