A Case of CD5-Positive Primary Cutaneous Diffuse Large B-Cell Lymphoma, Leg Type Secondary to Chronic Lymphedema.

Primary cutaneous lymphoma occurring at the site of lymphedema is a rare complication. A total of 13 cases of primary cutaneous lymphoma associated with chronic lymphedema have been reported in international studies. We reported a case of cutaneous diffuse large B-cell lymphoma (DLBCL) (leg type) secondary to chronic lymphedema of the lower limbs. Histopathology showed hyperkeratosis of epidermis, acanthosis, and significant edema in the superficial dermis, with diffuse mononuclear infiltration in the dermis. Immunohistochemical studies revealed the expression of CD5, CD20, Pax-5, Bcl-2, Bcl-6, MUM-1, c-myc, and Ki-67. Therefore, the diagnosis of cutaneous DLBCL (leg type) was made. The study further confirmed the association between lymphoma and lymphedema. Especially, it showed CD5 expression. CD5-positive DLBCLs is a specific subgroup of DLBCLs, only approximately 10% of DLBCLs express CD5.