Segment-specific patterns of regional lymph-node metastasis in primary small-cell carcinoma of the esophagus: A systematic review and meta-analysis - Ke-Xun Li; Jie Mao; Jian-Zhe Zhang; Zi-Long Qian; Yong-Tao Han; Xue-Feng Leng (World Journal of Clinical Oncology, 2026)