Abstract: A 55-year-old female presented with nodule behind the right ear for half a year. Skin biopsy revealed that a large number of medium-size lymphocytes infiltrated in the dermis and around the skin appendages, with mild atypia, and small lymphocytes and histological cells were seen. Immunohistochemistry examination showed that CD4 (+), CD8 (+, a few cells), CD2 (+), CD20 (+), CD3 (+), CD79a scattered (+), CD5 (+), CD7 (+), Ki-67 (+, < 5%). The clonal amplification peak was found in the target band by TCRG gene rearrangement detection. The diagnosis of primary cutaneous CD4⁺ small/medium T-cell lymphoproliferative disorder was made.

Key words: lymphoproliferative disorder, primary cutaneous lymphoma, T-cell lymphoma, CD4⁺