1Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing, Jiangsu 210042, China. 2Department of Dermatology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi 030001, China

Introduction Primary cutaneous marginal zone B-cell lymphoma(PCMZL) is one of the most common cutaneous B-cell lymphomas. Some cases were reported to be associated with spirochetal infection. It commonly occurs in 50��60 years old patients, and the male-to-female ratio is (1.5-2)��1. PCMZL presents with red to violet papules, plaques or nodules, and usually involves trunk (46%), upper limbs (17%) or head (13%). Occurence of single lesion is more common compared to multiple lessions. Patients with PCMZL usually have no night sweats, fever, weight loss or other constitutional symptoms (B symptoms)[2]. In terms of histology, the epidermis of patients with PCMZL is usually normal, however, dermis and subcutaneous fat is commonly involved by forming nodular or diffuse infiltrates. Tumor cells are composed of small lymphocytes, marginal zone B cells (centrocyte-like cells), lymphoplasmacytoid cells, and plasma cells, and intermingle with a small number of centroblast- or immunoblast-like cells and many reactive T cells. Reactive germinal centers frequently appear, surrounded by marginal zone B cells. Tumor cells express CD20, CD22, CD79a, and Bcl-2, while are negative for CD5, CD10 and Bcl-6.