The most common pathological type of esophageal cancer is squamous cell carcinoma, while adenocarcinoma is relatively rare, accounting for about 5%-10% of esophageal cancers. Most adenocarcinomas occur on the basis of Barrett’s esophagus, morphologically similar to gastrointestinal adenocarcinomas, and sometimes lesions of Barrett’s esophagus with dysplasia can be seen adjacent to the cancer. In addition, there are some rare types of adenocarcinomas. Based on a comprehensive review of the literature, they are briefly described below.
Adenoid cystic carcinoma often occurs in the distal esophagus,with no apparent gender predominance.Its characteristic is the formation of well-formed, regular glands (cribriform pattern) by tumor epithelial islands containing mucin.Its morphological features are similar to adenoid cystic carcinoma of the parotid gland and will not be elaborated further.It is generally believed that adenoid cystic carcinoma originates from submucosal ducts or glands, but in many cases, the cancerous tissue is associated with dysplasia or carcinoma in situ of the squamous epithelium, or directly continuous with it. This indicates that at least some tumors originate from squamous epithelium, possibly due to variants or metaplasia of squamous cell carcinoma.Some early adenocarcinomas originating from submucosal glands may be accompanied by squamous carcinoma in situ, so the origin remains controversial.The prognosis of adenoid cystic carcinoma is not worse than that of ordinary squamous cell carcinoma or basaloid squamous cell carcinoma.
Mucoepidermoid carcinoma is believed to originate from esophageal glands and is often confused with adenosquamous carcinoma.In typical mucoepidermoid carcinoma, some areas show obvious squamous differentiation (epidermoid carcinoma) but contain glandular components and mucin secretion.The glandular components sometimes appear as well-formed glands, but atypical cell clusters can also be seen. Intracellular mucin can be demonstrated by PAS staining at pH 2.5, Alcian blue staining, or mucicarmine staining.Intimate mixing of squamous cells and mucin-secreting cells can be seen in the tumor, but in adenosquamous carcinoma, there is no such intimate mixing of these two components. This feature can serve as a reference for differentiation.
Submucosal Gland Adenocarcinoma
This extremely rare salivary gland-type tumor can occasionally be seen in the esophagus, with typical manifestations including adenoid cystic carcinoma and mucoepidermoid carcinoma.Unlike salivary gland tumors, these tumors are aggressive like other esophageal cancers and can be rapidly fatal.They may originate from submucosal glands of the esophagus, mainly based on their submucosal location or being covered by intact squamous epithelium.Adenocarcinoma in situ occurring in submucosal glands is relatively easy to identify, while invasive adenocarcinoma is more difficult to determine whether it originates from submucosal glands.
Adenocarcinoma in Heterotopic Gastric Mucosa
Heterotopic gastric mucosa is relatively common in autopsy or endoscopic examinations.Most patients are asymptomatic, but some complain of dysphagia, and extra-esophageal manifestations such as hoarseness and cough.Ulceration, stricture, or esophagotracheal fistula rarely occur in this mucosa.Ulcers may originate from peptic ulcers located distal to the heterotopic mucosa.Adenocarcinoma in heterotopic gastric mucosa is considered a source of upper esophageal adenocarcinoma.Its pathological appearance is not significantly different from general adenocarcinoma, but the presence of heterotopic gastric mucosa adjacent to the cancer is an important basis for diagnosis.This malignant transformation through intestinal metaplasia and dysplasia may occur in larger areas of heterotopia but is very rare.It is reported that in this adenocarcinoma, both CK7 and CK20 show immunoreactivity for intestinal metaplasia, which is also a common pattern in Barrett’s esophageal mucosa.
The first three types of adenocarcinoma mentioned above can be considered as salivary gland-type adenocarcinomas of the esophagus. The fourth type is caused by dysplasia on the basis of heterotopic gastric mucosa. To determine whether adenocarcinoma originates from Barrett’s esophagus, submucosal salivary gland-like glands, or heterotopic gastric mucosa, the key is adequate sampling to discover its primary or early lesions, such as dysplasia in Barrett’s esophageal mucosa or heterotopic gastric mucosa, and early cancerous changes in submucosal glands.
Source: Huaxia Pathology Network
