Abstract: A 60-year-old man presented with red plaque on the right chest for 2 months. Histopathology showed that the epidermis was almost normal, and the proliferation of small to medium lymphoid cell in dermis, with infiltrating skin appendages. The tumor cells were small to medium in size, the nuclei were hyperchromatic and slightly irregular, and mitotic figures were not obvious, and a few large cells were scattered. Immunohistochemistry showed that the lesion cells were diffusely positive for CD3, CD4 and CD5, and some were positive for PD-1, the positive staining rate for Ki-67 was 20%, T-cell receptor gene rearrangement showed positive result. A diagnosis of primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder was made. Surgical resection was performed.

Key words: primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder