Cutaneous mast cell tumours (MCTs) are the most frequent malignant skin tumours in dogs. Mutations in the c‐KIT proto‐oncogene are correlated with the pathogenesis and aggressiveness of MCTs. To date, studies have focused on c‐KIT mutations and KIT protein localization, with a general lack of mRNA‐level analyses. In this study, c‐KIT mRNA expression was investigated in canine MCTs by RNA in situ hybridization (RNA‐ISH). Furthermore, we evaluated associations between c‐KIT mRNA expression and the histological grade, KIT immunohistochemical staining pattern and other clinicopathological parameters. c‐KIT mRNA expression was observed in all MCT samples, appearing as clusters of dots in the cytoplasm of neoplastic cells. A significant correlation was detected between c‐KIT mRNA expression (quantified according to the H‐score and the percentage of positive cells) and the histological grade (determined using two‐and three‐tier grading systems; P < .05). We also found a significant positive correlation (all P < .05) between c‐KIT mRNA expression and the proliferation indices (mitotic index, Ki‐67, and Ag67). However, no significant associations with c‐KIT expression from RNA‐ISH were found with respect to different KIT staining patterns. Overall, these results demonstrate that c‐KIT mRNA expression might be an additional tool for measuring the c‐KIT status in canine cutaneous MCTs and could serve as a potential prognostic factor. Further studies should evaluate the prognostic significance of c‐KIT mRNA expression in a large and uniform cohort of canine MCTs.

中文翻译：

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犬皮肤肥大细胞肿瘤的原位 c-KIT mRNA 定量及其与预后因素的关系

皮肤肥大细胞瘤（MCT）是犬最常见的恶性皮肤肿瘤。c - KIT原癌基因的突变与 MCT 的发病机制和侵袭性相关。迄今为止，研究主要集中在 c- KIT突变和 KIT 蛋白定位上，普遍缺乏 mRNA 水平的分析。在这项研究中，通过 RNA 原位杂交 (RNA-ISH) 研究了犬 MCT 中c- KIT mRNA 的表达。此外，我们评估了 c- KIT mRNA 表达与组织学分级、KIT 免疫组织化学染色模式和其他临床病理参数之间的关联。c- KIT在所有 MCT 样品中观察到 mRNA 表达，在肿瘤细胞的细胞质中表现为点簇。在 c- KIT mRNA 表达（根据 H 分数和阳性细胞百分比量化）和组织学分级（使用两级和三级分级系统确定；P  < .05）之间检测到显着相关性。我们还发现 c- KIT mRNA 表达与增殖指数（有丝分裂指数、Ki-67 和 Ag67）之间存在显着的正相关（所有P <.05 ）。然而，对于不同的 KIT 染色模式，未发现与来自 RNA-ISH 的c - KIT表达有显着关联。总的来说，这些结果表明 c- KITmRNA 表达可能是测量犬皮肤 MCT 中c- KIT状态的额外工具，并可作为潜在的预后因素。进一步的研究应该评估 c- KIT mRNA 表达在大型和统一的犬 MCT 队列中的预后意义。