An 81-year-old white woman with a past medical history significant for coronary artery disease and a cerebrovascular accident presented with a large ulcerated tumor on her left ankle of 3 months duration. A skin biopsy was reported as diffuse large B-cell lymphoma. The histology revealed a diffuse infiltrate composed of a monotonous population of large round lymphocytes with features of centroblasts and immunoblasts. Immunostaining showed that the tumor cells were positive for CD20, MUM-1, FOX-P1, IgM, and BCL2 but negative for CD30. Immunostaining for Ki-67 showed that the tumor cells had a high proliferative index. The lesion was treated with radiotherapy, but the patient died 8 months later. There are 3 main types of primary cutaneous B-cell lymphoma: primary cutaneous marginal zone lymphoma, primary cutaneous follicle center lymphoma, and primary cutaneous diffuse large B-cell lymphoma, leg type (PCLBCL-LT). Primary cutaneous marginal zone lymphoma and primary cutaneous follicle center lymphoma are indolent lymphomas with a 5-year disease-specific survival greater than 95%, whereas PCLBCL-LT represents a more aggressive type of disease with a 5-year disease-specific survival of approximately 50%. PCLBCL-LT has a phenotype similar to the “activated” subtype of nodal diffuse large B-cell lymphoma, which is thought to be a reason for the poor prognosis. The treatment of patients with PCLBCL-LT should be aggressive and polychemotherapy is indicated in most cases.