Primary cutaneous DLBCL non-GCB type: challenges of a rare case

Several types of B-cell lymphomas, including both primary cutaneous lymphomas and systemic lymphomas, may affect the skin, with partially overlapping clinical, morphological and immunohistochemical features. Currently, the World Health Organization (WHO) classification of primary cutaneous B-cell lymphomas does not include diffuse large B-cell lymphomas (DLBCL) and considers leg-type DLBCL the only primary cutaneous DLBCL. Here we report the case of a 72-year-old white woman with a primary cutaneous neoplasm comprised of large cells with round nuclei, irregularly clumped chromatin and one or more inconspicuous nucleoli. The immunohistochemistry demonstrated positivity for CD20 and MUM1, with no significant genetic translocations detected by fluorescence in-situ hybridization. After staging, we considered this neoplasm a primary cutaneous DLBCL with a non-germinal center phenotype, not otherwise specified, inconsistent with a leg-type DLBCL. Because of this view, we underscore the need for greater knowledge of the molecular landscape of B-cell lymphomas in order to reconsider the classification of such neoplasms in the skin.