Mezzalira Giorgia, Martini Valeria, Abramo Francesca, Iussich Selina, Orlandi Margherita, Pazzini Luca, Banco Barbara, Rambaldi Anna Maria, Bisognoso Alessandro, Arena Filippo, Cocciolo Giulio, Marino Michele, Massaro Maria, Aresu Luca
MYLAV La Vallonea Veterinary Diagnostic Laboratory, Milan, Italy.
Department of Veterinary Medicine and Animal Sciences, University of Milan, Lodi, Italy.
Front Vet Sci. 2025 Apr 22;12:1578425. doi: 10.3389/fvets.2025.1578425. eCollection 2025.
Recent investigations have identified rare, phenotypically complex lymphoma variants, including cases exhibiting concurrent expression of T- and B-cell markers. These atypical presentations suggest perturbations in lymphoid differentiation programs or clonal evolution, necessitating more sophisticated diagnostic approaches. The concurrent expression of CD3 and CD20 in canine lymphomas represents a particularly compelling phenomenon documented across various anatomical sites. Molecular diagnostics, particularly PCR for Antigen Receptor Rearrangements (PARR), have provided crucial insights into these phenotypically complex cases, revealing concurrent clonal rearrangements of both TCRγ and IgH in selected cases, further challenging traditional classification paradigms.
Here, we report 33 cases of canine double-positive lymphoma, retrieved with a retrospective analysis of the MyLAV Diagnostic Laboratory electronic database. Specifically, we report results of an integrated approach combining WHO-based morphological classification, comprehensive immunohistochemical immunophenotyping with T-cell (CD3 and CD5) and B-cell markers (CD20 and PAX5), and PARR analysis.
The skin, oral/nasal mucosa and mucocutaneous junction were the most commonly affected sites, accounting for 24 cases (72.7%). All cases stained positive for CD3 and CD20 (100%), 32 (97%) for CD5, and only 12 (36.4%) for PAX5. Aberrant cytoplasmic localization of CD20 was found in 29 (87.9%) cases. Molecular analysis revealed rearrangement signals of TCR gene in 23 of 33 cases (69.7%) and of CBmajor or CBminor gene in 9 (27.3%).
The findings emphasize that while immunohistochemistry remains a fundamental diagnostic tool, it may be insufficient in isolation for definitive lineage determination in these cases. PARR analysis emerges as an essential complementary technique for distinguishing between aberrant marker expression and true biphenotypic differentiation.
最近的研究发现了罕见的、表型复杂的淋巴瘤变体，包括同时表达T细胞和B细胞标志物的病例。这些非典型表现提示淋巴样分化程序或克隆进化存在紊乱，因此需要更复杂的诊断方法。犬淋巴瘤中CD3和CD20的同时表达是一种特别引人注目的现象，在各个解剖部位均有记录。分子诊断，尤其是抗原受体重排的聚合酶链反应（PARR），为这些表型复杂的病例提供了关键见解，揭示了部分病例中TCRγ和IgH同时发生克隆重排，这进一步挑战了传统的分类模式。
在此，我们报告了33例犬双阳性淋巴瘤病例，通过对MyLAV诊断实验室电子数据库进行回顾性分析获得。具体而言，我们报告了一种综合方法的结果，该方法结合了基于世界卫生组织的形态学分类、使用T细胞（CD3和CD5）和B细胞标志物（CD20和PAX5）进行的全面免疫组化免疫表型分析以及PARR分析。
皮肤、口腔/鼻腔黏膜和黏膜皮肤交界处是最常受累的部位，占24例（72.7%）。所有病例CD3和CD20染色均呈阳性（100%），CD5阳性32例（97%），PAX5阳性仅12例（36.4%）。29例（87.9%）病例中发现CD20存在异常胞质定位。分子分析显示，33例中有23例（69.7%）存在TCR基因重排信号，9例（27.3%）存在CBmajor或CBminor基因重排信号。
研究结果强调，虽然免疫组化仍然是一种基本的诊断工具，但在这些病例中，仅靠免疫组化可能不足以确定确切的谱系。PARR分析成为区分异常标志物表达和真正双表型分化的重要补充技术。
