假性乳糜胸是一种罕见的疾病。其特征是乳白色胸腔积液，胆固醇/甘油三酯比率>1。根据已发表的报告，大多数患者患有相关疾病，包括类风湿性关节炎和结核病，只有一名患者患有与肺转移相关的口咽癌。在此，我们描述了类风湿性关节炎和肺鳞状细胞癌患者假性乳糜胸的发展。胸腔积液中确认有癌细胞，但肺野或胸内淋巴结未见癌浸润或结核相关病变引起的胸导管损伤。抗癌治疗包括免疫检查点抑制剂，肿块内空洞的出现和气胸与肺癌治疗有关。尽管假性乳糜胸的发病机制尚不清楚，但我们相信这一临床病程将为未来具有类似病程的患者的治疗提供一些提示性信息。

Pseudochylothorax is a rare disease entity. It is characterized by a milky white pleural fluid with a cholesterol/triglyceride ratio >1. According to published reports, most patients had associated diseases, including rheumatoid arthritis and tuberculosis, with only one patient having oropharynx carcinoma associated with lung metastases. Herein, we describe the development of pseudochylothorax in a patient with rheumatoid arthritis and lung squamous cell carcinoma. Cancer cells were confirmed in the pleural fluid, but there was no thoracic duct damage caused by cancer invasion or tuberculosis-related lesions in the lung field or intrathoracic lymph nodes. Anticancer treatment included immune checkpoint inhibitors, and the appearance of a cavity within the mass and pneumothorax were associated with lung cancer treatment. Although the mechanism of pseudochylothorax onset was unknown, we do believe that this clinical course would provide some suggestive information on treatment for patients with a similar course in the future.