Pathology

Superficial esophageal cancers are classified into three major types including Type 0-I (superficial and protruding type including Type 0-Ip (pedunculated) and Type 0-Is (sessile)), Type 0-II (superficial and flat type including Type 0-IIa (slightly elevated), Type 0-IIb (flat), and Type 0-IIc (slightly depressed)), and Type 0-III (superficial and excavated type). More protruded (Type 0-I) or more depressed (Type 0-III) lesions are associated with deeper invasion in the submucosa. All submucosal cancers have a substantial risk of lymph node metastases. Consequently, intraepithelial carcinoma or carcinoma invading the lamina propria is generally treated by endoscopic resection. Advanced esophageal cancers are classified into five types, including Type 1 (protruding type), Type 2 (ulcerative and localized type), Type 3 (ulcerative and infiltrative type), Type 4 (diffusely infiltrative type), and Type 5 (unclassified type). The two most frequent types are Types 2 and 3. Iodine staining method is useful not only for optimal visualization of esophageal squamous mucosal abnormalities but also for detecting groups at high risk of multicentric cancer in the upper aerodigestive tract. Clinicopathologic prognostic factors include TNM stage, lymph node metastasis, tumor invasion depth, lympho-vascular invasion, intramural metastasis, tumor vascularity, infiltrating growth pattern, inflammatory response, tumor budding, tumor nest configuration, pathologic response to neoadjuvant therapy, completeness of surgical resection, patient’s general health condition, and PD-1 and PD-L1 expression level. The subtypes of esophageal squamous cell carcinoma include basaloid squamous cell carcinoma, carcinosarcoma/spindle cell squamous cell carcinoma/sarcomatoid carcinoma, adenosquamous carcinoma, and verrucous carcinoma.