Update on T-Cell Lymphoma Epidemiology.

PURPOSE OF REVIEW: T-cell lymphomas (TCLs) are a group of rare subtypes of non-Hodgkin lymphoma derived from mature T-lymphocytes. Recent updates in lymphoma classification based on the cell-of-origin pathogenesis have shed new light on TCL epidemiology and outcomes. Contemporary regional consortia and international studies, including those conducted recently in Asia and South America, have provided an updated delineation of the major subtypes across various global regions. RECENT FINDINGS: Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), remains the most common subtype globally except in Asia, where extra-nodal NK-T cell lymphoma (ENKTL) has emerged as the most prevalent. Angioimmunoblastic T-cell lymphoma (AITL) is the second most common subtype globally except in South America where its incidence falls behind adult T-cell leukemia/lymphoma (ATLL) and ENKTL. ALK-negative anaplastic large cell lymphoma (ALCL) has been recognized as the second most common subtype in some parts of South America. Studies on the newly classified breast implant-associated ALCL (BIA-ALCL) are beginning to reveal its distribution and risk factors. Deciphering the epidemiology of TCLs is a challenging endeavor due to the rarity of these entities and ongoing refinement in classification. Collaborative efforts on prospective registries based on the most current WHO classifications will help capture the true epidemiology of TCL subtypes to better focus resources for diagnostic, prognostic, and therapeutic efforts.

Primary cutaneous marginal zone lymphoproliferative disorder following COVID-19 vaccination.

During the coronavirus disease 2019 (COVID-19) pandemic, COVID-19 vaccines were administered worldwide. A number of skin reactions, including primary cutaneous T-cell lymphoproliferative disorders (LPDs) were reported following COVID-19 vaccination. We report a case of primary cutaneous marginal zone lymphoproliferative disorder (PCMZLPD) secondary to COVID-19 vaccination. A 57-year-old man presented with an erythematous nodule on his left arm at the site of vaccine inoculation following his first dose of the Moderna (mRNA-1273) vaccine a few weeks prior. The nodule continued to progress in size after the second dose. A skin biopsy specimen of the nodule showed a diffuse dermal infiltrate of small to medium-sized lymphocytes with plasma cells and histiocytes. The infiltrate was composed of CD3+ T cells with CD20+ and CD79a+ B cells. The neoplastic B cells reacted with BCL-2 and were negative for BCL-6 and CD10. Kappa light chain restriction was identified by in situ hybridization. Gene rearrangement studies revealed kappa light chain monoclonality, confirming the diagnosis of PCMZLPD. The temporal association with the Moderna vaccination and the occurrence of the lesion at the inoculation site indicate a COVID-19 vaccination-induced PCMZLPD. This is one of the rare cases of PCMZLPD following COVID-19 vaccination.