尽管ICR小鼠中已有肺腺瘤的报道，但年龄≤10周的小鼠中尚未报道自发性腺瘤。在这里，我们报告了一只 10 周龄雄性 ICR 小鼠的左侧叶外周病变中存在一个边界清楚的结节（1 mm × 1 mm）。组织病理学评估显示界限清楚的结节压迫周围组织。肿瘤细胞呈多角形，细胞边界不明显，细胞核圆形/椭圆形，细胞质丰富。这些特征导致 II 型细胞源性细支气管肺泡腺瘤的诊断。鉴于它们通常在老年实验动物中观察到，该病例代表了青春期前年轻实验小鼠自发性肿瘤的罕见表现。

Although pulmonary adenomas have been reported in ICR mice, spontaneous adenomas have not been reported in mice aged ≤10 weeks. Here, we report a well-circumscribed nodule (1 mm × 1 mm) in the peripheral lesion of the left lateral lobe of a 10-week-old male ICR mouse. Histopathologic evaluation revealed a well-demarcated nodule compressing the surrounding tissue. The neoplastic cells were polygonal with indistinct cellular borders, round/oval nuclei and abundant cytoplasm. These characteristics led to the diagnosis of type II cell-derived bronchioloalveolar adenoma. Given that they are generally observed in aged laboratory animals, this case represents a rare manifestation of a spontaneous tumor in young laboratory mice before puberty.