Cutaneous T-cell lymphoma (CTCL), rare subtypes: five case presentations and review of the literature.

The vast majority of cutaneous T-cell lymphomas (CTCL) are encompassed by mycosis fungoides and CD30+ lymphoproliferative disorder (LPD), however rare distinct CTCLs have been defined. The current edition of the World Health Organization (WHO) includes 12 CTCL subtypes with discrete diagnosable clinical, histologic and phenotypic features. The rarest subtypes, i.e. those that comprise <1% to 2%, include indolent entities, such as primary cutaneous CD4+ small/medium T-cell LPD (SMPTC-LPD), primary cutaneous acral CD8+ T-cell lymphoma (acral CD8+ TCL) and subcutaneous panniculitis-like TCL (SPTCL) and aggressive entities, such as primary cutaneous CD8+ aggressive epidermotropic cytotoxic T-cell lymphoma (CD8+ PCAETL) and primary cutaneous gamma /delta T-cell lymphoma (PCGDTCL). Case presentations, clinical features, and treatment approaches for these five rare CTCL subtypes will be reviewed.