Upregulation of inhibitory signaling receptor programmed death marker-1 (PD-1) in disease evolution from cutaneous lymphoid dyscrasias to mycosis fungoides and Sezary's syndrome

PD-1 seems to correlate with disease progression in epitheliotropic T cell dyscrasias ranging from minimal staining in prelymphomatous dyscrasias to significant staining in MF, likely reflecting the effects of PD-1 on inhibiting tumor surveillance regulatory T cell populations. PD-1 was consistently expressed in MF while it was consistently negative in primary CD30 + LPD, suggesting the possibility of using PD-1 as a means of distinguishing CD30 + MF from primary cutaneous ALCL.