Primary Cutaneous Diffuse Large B-cell Lymphoma, Leg Type

Primary cutaneous B-cell lymphomas (PCBCLs) are a heterogenous group of mostly low-grade B-cell lymphomas (exceptions exist) that involve skin with no evidence of extracutaneous disease at presentation. They are less common than cutaneous T-cell lymphomas and make up 20-25% of all primary cutaneous lymphomas. The 2018 WHO-EORTC update of classification of primary cutaneous lymphomas includes the following PCBCLs:

• cutaneous follicle center lymphoma
• cutaneous marginal zone lymphoma
• cutaneous diffuse large B-cell lymphoma - leg type

PCBCLs must be distinguished from systemic B-cell lymphomas with secondary skin involvement as the biologic behavior, treatment, and prognosis are completely different for the two groups. Examples: mantle cell lymphoma, B-CLL/SLL, lymphomatoid granulomatosis, plasmablastic lymphoma, and post-transplant lymphoproliferative disorder. Intravascular large B-cell lymphomas can present with disease limited to skin. EBV+ mucocutaneous ulcer, a recently recognized entity, presents with ulceration of skin, oropharyngeal mucosa, or GI tract in immunocompromised host. References:1. Jaffe, ES et al (2017). Hematopathology - Second Ed. Philadelphia, PA. Elsevier.2. Swerdlow, SH et al (2017). WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues, Revised 4th Ed.; IARC, Lyon, France.3. Calonje, E et al (2020). McKee's Pathology of the Skin with Clinical Correlations - 5th Ed. Elsevier.4. Skala SL, Hristov B, Hristov AC. Primary Cutaneous Follicle Center Lymphoma. Arch Pathol Lab Med. 2018;142:1313-1321.5. Dumont M et al. Diagnosis and Treatment of Primary Cutaneous B-Cell Lymphomas: State of the Art and Perspectives. Cancers 2020, 12, 1497.