Key Points

• Squamous cell carcinoma (SCC) and adenocarcinoma (AC), two major histologic subtypes of esophageal cancer, differ in presentation and prognosis but have overlapping diagnostic and staging protocols.
• The number of positive lymph nodes and the presence of distant metastasis are the most important prognostic clinical markers of esophageal cancer.
• The American Joint Committee on Cancer defines clinical classification (i.e., cTNM) based on clinical and radiologic data and is not dependent on tumor grade or location. Esophageal cancer is classified by clinical assessment, contrast studies, esophagoscopy, endoscopic ultrasonography, and positron emission tomography combined with computed tomography.
• Pathologic classification of esophageal cancer (i.e., pTNM) takes into account the tumor grade for both AC and SCC, as well as, the anatomical location for SCC. pTNM supplements cTMN with information acquired from specimen histology.
• Post chemo-radiation treatment clinical staging is termed ycTNM.
• Pathologic classification after multimodality therapy (i.e., ypTNM) is uniquely described in the 8^th edition of the American Joint Committee on Cancer.

Esophageal cancer is the 8^th most common type of cancer worldwide and ranks 6^th in annual cancer-related deaths.[1] Most malignant esophageal tumors are either SCC or AC. A minority of these tumors include extra-pulmonary small cell cancer and mesenchymal tumors (most commonly leiomyomas).[2] The incidence of AC has surpassed SCC, making it the most prevalent type of esophageal cancer in the Western world. AC is associated with a rapidly increasing incidence of tumors at the esophagogastric junction (EGJ) and gastric cardia.[3] The two major histologic types of esophageal cancer differ significantly in presentation. SCC is dominant in socioeconomically poorer populations of the Eastern world and is usually associated with significant weight loss, whereas esophageal AC is a disease of the affluent, often overweight population. Esophageal AC is rarely associated with significant constitutional symptoms at presentation.

Despite the variation in histologic types, the diagnostic and staging criteria for both of these types of cancer overlap and are discussed in detail in this chapter. The new TNM staging system (referring to Tumor, lymph Nodes, and Metastasis) was recently introduced by the American Joint Committee on Cancer (AJCC 8^th ed., 2017).[4] In this chapter, the 8^th edition parameters and guidelines will be discussed and compared to those set forth in the 7^th edition.[5]