Mast cell (MC) is an important player in the development of skin diseases, including atopic dermatitis, psoriasis, and urticaria. It is reported that MC infiltration and activation are observed around various types of tumors and speculated that MCs play key roles in their pathogenesis. As MCs in human seborrheic keratosis (SK) have not been well investigated, here we focused on the MCs in SK. The number of c-Kit and tryptase-positive MCs was significantly increased around the SK compared with the marginal lesion. Degranulated MCs were also increased around the tumors. Furthermore, MC growth factor, stem cell factor (SCF), expression within the SK was significantly upregulated compared with the marginal lesion. Interestingly, one of the cognitive regulators of SCF expression, cannabinoid receptor type 1 (CB1) immunoreactivity was downregulated within the SK. Our results suggest that MCs play important roles in the pathogenesis of SK and that SCF can be also deeply involved in the development of SKs. Our current results highlight the CB1–SCF–MC interaction as a novel mechanism of SK development and this also will be utilized for developing a novel treatment.

肥大细胞（MC）是包括特应性皮炎，牛皮癣和荨麻疹在内的皮肤疾病发展的重要参与者。据报道，在各种类型的肿瘤周围观察到MC的浸润和激活，并推测MC在其发病机理中起关键作用。由于尚未对人类脂溢性角化病（SK）中的MC进行深入研究，因此我们将重点放在SK中的MC。与边缘病变相比，SK周围的c-Kit和类胰蛋白酶阳性MC的数量显着增加。颗粒周围的MC也增加了。此外，与边缘病变相比，SK中MC生长因子，干细胞因子（SCF）的表达显着上调。有趣的是，SCF表达的认知调节器之一 SK中的大麻素1型受体（CB1）免疫反应性下调。我们的结果表明，MCs在SK的发病机理中起着重要作用，而SCF也可以深入参与SKs的发展。我们目前的结果突出了CB1-SCF-MC相互作用作为SK发生的新机制，这也将用于开发新的治疗方法。