Hypopigmented interface T‐cell dyscrasia: A form of cutaneous T‐cell dyscrasia distinct from hypopigmented mycosis fungoides

Hypopigmentation in cutaneous T‐cell lymphoproliferative disease should not always be equated with hypopigmented mycosis fungoides (MF). A form of hypopigmented pre‐lymphomatous T‐cell dyscrasia falling under the designation of the so‐called hypopigmented interface variant of T‐cell dyscrasia has recently been proposed. The aim of the present study was to establish hypopigmented interface T‐cell dyscrasia as its own entity apart from other T‐cell dyscrasias and MF using a patient case series. Twenty four cases of hypopigmented interface T‐cell dyscrasia were identified in the dermatopathology database of Weill Medical College of Cornell University. There were 17 females and seven males (mean age, 36 years). In children and adolescents, the patients were most commonly of African American extraction. Truncal photo‐protected areas manifesting as large solitary patches or multiple smaller macules were characteristic; disease progression to MF occurred in only one patient. The lesions responded to topical steroids and light therapy. The pathology was defined by a cell poor interface associated with degeneration of keratinocytes and melanocytes, and by lymphocytes whose nuclei showed low‐grade cerebriform atypia, and which expressed a significant reduction in CD7 and CD62L expression. In 50% of the cases, the implicated cell type was of the CD8 subset. Clonality was not identified. Hypopigmented interface T‐cell dyscrasia is a distinct entity separate from and rarely progressive to MF.