Primary Cutaneous B-Cell Lymphomas: An Update

Abstract

Primary cutaneous B-cell lymphomas (PCBCLs) comprise a group of extranodal B-cell non-Hodgkin lymphomas B-cell derived, which primarily involve the skin without evidence of extracutaneous disease at the time of diagnosis. They include ~25% of all cutaneous lymphomas and are classified in three major subgroups (World Health Organization (WHO) 2017): primary cutaneous marginal zone lymphoma (PCMZL), primary cutaneous follicle-center cell lymphoma (PCFCL), and diffuse large B-cell lymphoma, leg type (PCDLBCL, LT). This classification also includes some less common entities such as intravascular large B-cell lymphoma. Recently, WHO-EORTC added Epstein-Barr virus positive (EBV+) mucocutaneous ulcer, as a new provisional distinct entity, to cutaneous B-cell lymphomas. PCBCLs are classically characterized by patches, plaques, or nodules showing great variability for color, shape, and location. Diagnosis requires histological examination with immunohistochemical staining. In general, therapeutic options depend on the exact histological and immunohistochemical classification, disease presentation, and risk assessment. PCMZL and PCFCL are considered indolent lymphomas with a good prognosis and are associated with 5-year disease-specific survival ≥ 95%. In contrast, PCDLBCL, LT is considered an aggressive lymphoma with a survival rate in 5 years of lower than 60%. Patients with a solitary lesion or limited lesions in a single anatomical site require different treatments as compared to patients with generalized lesions or refractory disease or extracutaneous involvement. Therapeutic choice includes observation, local, or systemic therapy based on histology and disease extension. Patient management is multidisciplinary, including dermatologists, pathologists, hemato-oncologists, and radiation oncologists.

Keywords: EBV-positive mucocutaneous ulcer; diffuse large B-cell lymphoma; intravascular large B-cell lymphoma; leg type; primary cutaneous follicle-center cell lymphoma; primary cutaneous marginal zone lymphoma.

Figure 1

Clinical (A) and dermoscopical (B) images of a PCMZL. Clinical (C) and dermoscopical (D) images of a PCFCL. Clinical (E) and dermoscopical (F) images of a PCDLBCL leg type.

Figure 2

Primary cutaneous germinal center cell lymphoma: histological findings. Histological examination showing a dense lymphoid infiltrate in dermis and hypodermis, organized in vaguely defined nodules. The lymphoid population infiltrates the hypodermis, entrapping adipocytes (A: H&E, 2×). The lymphoid nodules are constituted by large and irregular germinal centers (B: H&E, 40×) and are positive for bcl6 immunostaining (C: bcl6 immunostain, 10×). Primary cutaneous marginal zone lymphoma: histological findings. A diffuse lymphoid population in the reticular dermis, extending along a hair (D: H&E, 2×). The lymphoid population is heterogeneous, including mature lymphocytes, lympho-plasmacytoid cells, and plasma cells (E: H&E, 40×). CD21 immunostaining highlights a partially destroyed network of follicular dendritic cells (F: CD21 immunostain, 40×).