Architectural and antigenic features of follicular dendritic cells as a clue to the histogenesis of primary cutaneous B-cell lymphoma

Primary cutaneous B-cell lymphoma (CBCL) are B-cell non-Hodgkin’s lymphoma primarily presenting in the skin without any detectable extracutaneous lesion despite careful and complete staging procedures. Previous studies of our group indicate that CBCL should be considered as a unique type of a low grade lymphoma4 In fact, CBCL have: 1. non aggressive clinical behavior (mostly loco-regional extension, good response to local treatments, low tendency to spread, and excellent prognosis); 2. uniform immunophenotypic (CD5-, CD10-) and genotypic features of neoplastic B-cells (lack of bcl-2 gene rearrangement), and 3. histologic evidence of centrocyte-like (monocytoid, parafollicular) cells in their whole morphologic spectrum, plasma cells, reactive lymphoid follicles and lymphoepithelial lesions. These typical features are strikingly similar to those described in so-called MALT (Mucosa-Associated Lymphoid Tissue) lymphoma, suggesting the interpretation of CBCL as the cutaneous counterpart of MALT lymphoma, i.e., Skin-Associated Lymphoid Tissue (SALT)-related B-cell lymphoma. The close clinical, histologic, immunologic, and genotypic similarities of CBCL and MALT-lymphoma with monocytoid/parafollicular lymphoma suggest the hypothesis of a common marginal cell origin for these neoplasms.