Cutaneous pseudolymphoma—A review on the spectrum and a proposal for a new classification

Abstract

Cutaneous pseudolymphomas (PSLs) belong to a group of lymphocytic infiltrates that histopathologically and/or clinically simulate lymphomas. Different causative agents (e.g., Borrelia sp., injected substances, tattoo, arthropod bite) have been described, but in many cases no cause can be identified, hence the term idiopathic PSL. Clinicopathological correlation is important to make the diagnosis. Four main groups of cutaneous PSL can be distinguished based on histopathologic and/or clinical presentation: (a) nodular PSL; (b) pseudo-mycosis fungoides (pseudo-MF) and simulators of other CTCLs; (c) other PSL (representing distinct clinical entities); and (d) intravascular PSL. This article gives an overview of the histopathologic and clinical characteristics of cutaneous PSLs and proposes a new classification.

Idiopathic cutaneous T‐cell pseudolymphoma with prominent granulomatous reaction

“…Dear Editor, Cutaneous pseudolymphoma refers to reactive lymphoid proliferation simulating cutaneous lymphomas both clinically and histopathologically. 1 Various causes of cutaneous pseudolymphoma are known, but no trigger can be found in many cases, and those cases are designated as idiopathic cutaneous pseudolymphoma. 1 We report a case of idiopathic cutaneous T-cell pseudolymphoma associated with prominent granulomatous reaction.…”

“…1 Various causes of cutaneous pseudolymphoma are known, but no trigger can be found in many cases, and those cases are designated as idiopathic cutaneous pseudolymphoma. 1 We report a case of idiopathic cutaneous T-cell pseudolymphoma associated with prominent granulomatous reaction.…”

“…1 Various causes of cutaneous pseudolymphoma are known, but no trigger can be found in many cases, and those cases are designated as idiopathic cutaneous pseudolymphoma. 1 We report a case of idiopathic cutaneous T-cell pseudolymphoma associated with prominent granulomatous reaction.A 78-year-old man presented with a 2-month history of an asymptomatic cutaneous lesion on his left knee, which had been resistant to topical corticosteroid therapy. He denied any triggering events including an insect bite and a trauma.…”

Kappa and lambda immunohistochemistry and in situ hybridization in the evaluation of atypical cutaneous lymphoid infiltrates

“…While the precise ratios of kappa and lambda expressing cells that signify monotypia have not been defined, when a marked predominance of kappa or a predominance of lambda light chain expression is identified, a clonal population is presumed (kappa: lambda of ≥8‐10 8‐15 or < 0.1‐0.3 8,10‐18 ). In contrast, non‐neoplastic populations of B‐cells and plasma cells characteristically include a mixture of kappa and lambda‐positive cells, often with a slight kappa predominance (kappa: lambda of approximately 1‐4:1‐2) 9,10,19‐21 . As part of the American Society of Dermatopathology (ASDP) Appropriate Use Committee (AUC) Task Force, lymphoproliferative subgroup, three practicing, board‐certified dermatopathologists working in academic medical centers (N.C., A.H.) or a hybrid academic/private practice (U.S.), assessed the evidence‐based, peer‐reviewed literature from 1967 to 2018 on the utility of kappa and lambda IHC as compared to ISH in the evaluation of cutaneous B‐cell lymphomas, plasma cell neoplasms, and atypical cutaneous lymphoid infiltrates.…”

“…In contrast, non-neoplastic populations of B-cells and plasma cells characteristically include a mixture of kappa and lambda-positive cells, often with a slight kappa predominance (kappa: lambda of approximately 1-4:1-2). 9,10,[19][20][21] As part of the…”