Normal
Histology
The
esophagus consists of three layers: mucosa, submucosa, and muscularis. The
mucosa consists of epithelial lining containing nonkeratinizing, stratified
squamous epithelium with a layer of basal and parabasal cells. This layer is
naturally required to proliferate more often than other layers of the oesophagus
in accordance to necessary cell loss.
One can see on the left, stratified squamous nonKeratinizing epithelium and intermixed smooth and striated muscle in the middle and towards the right of the figure.
Squamous
cell carcinoma is derived from this layer. The sublayer, lamina propria,
contains vessels, connective tissue, lymphatics, inflammatory cells and
esophageal cardiac glands which are mucus secreting glands. Adenocarcinomas
arise from these glands. The submucosa contains dense connective tissue with
both lymph and blood vessels. Further esophageal mucus secreting glands are
contained in the submucosa. The outer layer, the muscularis, consists of two
muscle layers. The inner muscle layer fibers are arranged circumferentially and
the
outer layer, longitudinally. Compared to the remaining gastrointestinal tract,
the esophagus lacks a fourth serosal layer. Without the serosa covering,
neoplasms that arise in the esophagus can spread unimpeded to other tissues.
Squamous
Cell Carcinoma (Epidermoid Carcinoma)
Squamous
cell (epidermoid) carcinoma has been the more common cell-type of esophageal
cancers, accounting for almost 90%. However, in the last decade, the incidence
of adenocarcinoma has increased an approximate 10% per year. It is no longer the
leading form of oesophageal cancer.
Afro-Americans
are five times more likely to develop squamous cell carcinoma than other
socio-economic groups. Males are 4 to 6 times more likely than females.
Cigarette smoking and alcohol consumption are the two major causes of all types
of esophageal cancers, but they are more closely correlated with squamous cell
carcinoma than adenocarcinoma12.
Squamous
cell carcinoma arises from the mucosa of the esophagus. Histologically, it is
characterized by invasive sheets of cells that run together and are cohesive,
polygonal, oval or spindle-shaped with a distinct or ragged stromal-epithelial
interface.
Squamous cell carcinoma of the oesophagus
Squamous cell carcinoma of the oesophagus
Squamous
cell carcinoma of the oesophagus
Squamous
cell carcinoma in situ
High
power squamous cell carcinoma
Polypoid
tumor of squamous cell carcinoma with keratin pearl
Tumours of epidermoid carcinoma are located mainly in the thoracic oesophagus. Approximately 60% are found in the middle third and about 30% in the distal third. Neoplasms can be of four major types:
1)
Fungating-type: Predominantly intraluminal growth with surface ulceration and
extreme friability. This type frequently invades mediastinal structures. It is
present in 11 to 60% of cases.
2)
Ulcerating-type: Characterized by a flat based ulcer with slightly raised edges;
hemorragic and friable and surrounding induration and erythema. This is present
in 25 to 63% of patients.
3)
Infiltrating-type: A dense firm logitudinal and circumferential intramural
growth pattern. The infiltrating type is found in 15 to 26% of squamous cell
carcinoma tumors.
4)
Polypoid: Intraluminal polypoid growth with a smooth surface on a narrow stalk.
Two to 8% of cases have this type of tumor. A five year survival of 70% is
associated with the polypoid tumor compared to less than 15% five year survival
for other types.