Abstract
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.
Highlights
Diffuse large B-cell lymphoma (DLBCL) is an aggressive mature B-cell neoplasm that may occur in both lymphoid and extra-lymphoid locations [1]
The case we present highlights the difficulties in classifying some cases of cutaneous B-cell lymphomas in daily diagnostic practice, reflecting the rarity and heterogeneity of the disease
The previous World Health Organization (WHO) classification (2005) defined Primary cutaneous diffuse large B-cell lymphoma (PCDLBCL) as a distinct category with specific clinical and biological features, while this entity was subsequently deleted in the current WHO classification [17]
Summary
Diffuse large B-cell lymphoma (DLBCL) is an aggressive mature B-cell neoplasm that may occur in both lymphoid and extra-lymphoid locations [1]. ABC is characterized by a less favorable prognosis [2] As this distinction was built on gene-profiling studies that presupposed molecular analysis with non-routinely available diagnostic technologies, alternative algorithms based on immunohistochemistry have been proposed for use in daily practice. Primary cutaneous diffuse large B-cell lymphoma (PCDLBCL) is rare, and its exact incidence is still substantially unknown. When assessing a skin-localized B-cell lymphoma with large-cell morphology, one has to answer two fundamental questions: is it a primary cutaneous lymphoma or a cutaneous localization by a systemic lymphoma? The differential diagnosis between PCDLBCL and other primary cutaneous lymphomas with large-ell morphology, including PCFCCL and PCDLBCL-LT, may be challenging and has important clinical implications. A close professional cooperation between the dermatologist, pathologist and hematologist is always needed to ensure the correct answers [2]
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