Subcutaneous panniculitis-like T-cell lymphoma: redefinition of diagnostic criteria in the recent World Health Organization-European Organization for Research and Treatment of Cancer classification for cutaneous lymphomas.

Subcutaneous panniculitis-like T-cell lymphoma is a primary T-cell lymphoma that preferentially involves the subcutaneous tissue. Although subcutaneous panniculitis-like T-cell lymphoma has been recognized as a distinctive entity in the category of peripheral T-cell lymphoma in the World Health Organization classification, its diagnostic criteria has been redefined by the recent World Health Organization-European Organization for Research and Treatment of Cancer classification for primary cutaneous lymphomas. Subcutaneous panniculitis-like T-cell lymphoma is now restricted to primary cutaneous T-cell lymphoma expressing alphabeta T-cell receptor phenotype. These lymphomas are usually CD3(+), CD4(-), CD8(+), and CD56(-), and usually have an indolent clinical course. The clinicopathologic features, differential diagnosis, immunophenotypic characteristics, and molecular features of subcutaneous panniculitis-like T-cell lymphoma are presented in light of the recent World Health Organization-European Organization for Research and Treatment of Cancer classification.