The etiology of esophageal cancer is not yet fully understood, but it is currently believed to be associated with the combined effects of multiple factors.
I. Diet and Lifestyle Factors – The Core Contributors
(1) Long-term consumption of hot tea or scalding foods above 65°C directly burns the esophageal mucosa. Repeated injury and repair cycles predispose the tissue to malignant transformation. The World Health Organization has classified hot beverages above 65°C as a Group 2A carcinogen.
(2) Pickled and preserved foods (e.g., salted vegetables, cured meats) contain high levels of nitrites, which can be converted into the potent carcinogen nitrosamines.
(3) Aflatoxins in moldy foods are also well-established carcinogens.
(4) Smoking increases the risk of esophageal cancer by 3–8 fold, while heavy alcohol consumption increases the risk by 5 fold. When combined, the carcinogenic effects are synergistic and substantially amplified.
II. Nutritional Deficiencies and Trace Element Insufficiency
Dietary patterns in high-incidence areas are commonly characterized by inadequate animal protein intake, as well as deficiencies in vitamins A, B₂, C, and others. Deficiencies in trace elements such as molybdenum, iron, zinc, fluorine, and selenium in soil and water have also been indirectly linked to esophageal cancer.
Esophageal cancer demonstrates a notable familial aggregation pattern. In high-incidence areas, familial cases spanning three or more generations may be observed. Individuals with a family history of esophageal cancer have a 2- to 4-fold increased risk compared with the general population.
IV. Chronic Esophageal Conditions
Long-standing chronic inflammation and ulceration from caustic esophageal burns and strictures, achalasia, esophageal diverticula, and reflux esophagitis can stimulate esophageal epithelial hyperplasia, ultimately leading to malignant transformation.
Pathological Classification
In China, esophageal cancer most frequently occurs in the middle thoracic segment (approximately 53%), followed by the lower thoracic segment (33%), with the upper thoracic segment being the least common (14%).
Histologically, squamous cell carcinoma is the most prevalent type, while adenocarcinoma is relatively rare.
Pathological types of early esophageal cancer include the occult type (carcinoma in situ), erosive type, plaque type, and papillary type, among which the erosive and plaque types are more commonly observed.
Intermediate and advanced stages are classified by morphological characteristics into the medullary type (most common, accounting for 56%–61%), fungating type (12%–17%), ulcerative type (11%–13%), constrictive/sclerotic type, and unclassified type.
Spread and metastasis: In early and intermediate stages, esophageal cancer spreads primarily via direct intramural extension. Lymphatic metastasis is the most important route of dissemination. In advanced stages, hematogenous metastasis may occur, most commonly to the liver, as well as to the lungs, pleura, bones, and other sites.