Discrimination of PCFBCL from other cutaneous B-cell-rich inflammatory or neoplastic lymphoid infiltrates, i.e., B-cell pseudo-lymphoma, CD4+ T-cell lymphoproliferation, primary cutaneous diffuse large B-cell lymphoma (PCLBCL) and primary cutaneous marginal zone lymphoma (PCMZL), on histopathological grounds may be challenging [5,9]. This evidence concerns the gene CD4 and primary cutaneous marginal zone B-cell lymphoma.