The esophagus is covered with squamous cell epithelium and contains as the rest of the gastro-intestinal tract three layers. In addition to the mucosa, the wall consists of the sub-mucosa separated from the mucosa by a thin layer of muscle (muscularis mucosa) and the outermost muscularis propria with circular and longitudinal muscle fibers.
- Squamous cell dysplasia/Carcinoma in situ (low-grade or high-grade intraepithelial neoplasia)
- Barrett’s esophagus with or without dysplasia/Carcinoma in situ in glandular epithelium (low-grade/high-grade dysplasia)
Precursor lesions are classified as squamous cell dysplasia (intraepithelial neoplasia) of low-grade or high-grade type. These lesions can precede squamous cell carcinomas or occur synchronous close to the invasive carcinoma.
Barrett`s esophagus represents as gastric or intestinal metaplasia (transformation of normal type of epithelium). These changes can appear due to reflux of gastric fluid in the distal (lower) part of the esophagus. Dysplasia preferably appears in the intestinal metaplasia of Barrett’s esophagus. The epithelial grading is as follows; negative for dysplasia, indefinite for dysplasia, low-grade or high-grade dysplasia.
Dysplasia in Barrett’s esophagus can develop into adenocarcinoma.
Classification and grading
The predominant carcinomas of the esophagus are squamous cell carcinomas and adenocarcinomas. The TNM system is used in the classification of these tumors. These carcinomas are graded as well, moderately and low differentiated dependent on the similarity to corresponding normal epithelium.
Within the squamous cell carcinomas and adenocarcinomas there are some variants/subtypes. Verrucous, spindle cell and basaloid are rare subtypes of squamous cell carcinoma. Mucoepidermoid or adenoidcystic carcinomas are variants of adenocarcinoma.
Other rare tumors are small cell carcinoma, malignant melanoma and undifferentiated carcinoma. These carcinomas can be very difficult to separate from metastasis to esophagus.
Mesenchymal tumors are rare in esophagus, but when they appear, leiomyomas are more common than GIST (gastrointestinal stromal tumor), in contrary to other parts of G-I tract. Malignant lymphomas and endocrine tumors are quite rare in this location.
An operation specimen, including resection of the esophagus with tumor, should include the following information:
- Infiltration depth
- Circumferential margin
- Number of lymph nodes with and without metastasis
- Tumor relation to resection borders
- Vessel infiltration
- Perineural infiltration