A 6-mo-old female Beagle dog was inappetent and depressed. The radiographic, ultrasonographic, and computed tomographic examination of the chest revealed a 10 × 7 cm multicystic mediastinal structure interpreted as altered thymus, in association with moderate pleural effusion that laboratory tests confirmed as hemothorax. No history of trauma or anticoagulant drug intoxication was reported, and no coagulation disorders were detected. Afterward, medial cranial sternotomy was performed to remove the altered tissue. Histologically, this tissue was compatible with a thymic remnant, characterized by numerous cystic lesions, mostly blood filled and lined by flattened-to-cuboidal epithelial cells, occasionally projecting into the surrounding stroma, and forming cytokeratin-positive ribbons, trabeculae, and papillae. Lymphocytes were scant, and numerous areas of congestion and hemorrhage were present throughout the samples. This case of idiopathic thymic hemorrhage with cystic degeneration of the thymus and pseudoepitheliomatous hyperplasia was an incidental finding; the dog recovered from surgery uneventfully.

中文翻译：

---

比格犬幼犬的囊性胸腺变性伴假性上皮增生：一种特发性病变？

一只6个月大的雌性比格犬（Beagle）不能适应并沮丧。胸部X线，超声和计算机断层扫描检查显示，10×7 cm多囊纵隔结构被解释为胸腺改变，并伴有中度胸腔积液，经实验室检查证实为胸腔积血。没有外伤史或抗凝药物中毒的报道，也未发现凝结障碍。之后，进行内侧颅骨胸骨切开术以去除改变的组织。从组织学上讲，该组织与胸腺残液兼容，其特征是有许多囊性病变，大部分血液充填并排成扁平的至鳞状上皮细胞，偶尔伸入周围的基质中，并形成细胞角蛋白阳性的条带，小梁和乳头状。淋巴细胞少，整个样品中都存在大量的充血和出血区域。这是伴有胸腺囊性变性和假性上皮瘤样增生的特发性胸腺出血病例。那只狗从手术中恢复得很好。