pathology

Last edited 11/2020 and last reviewed 11/2020

95% of gastric carcinomas are adenocarcinomas. 64% of carcinomas are situated in the prepyloric region. There are three morphological forms:

• fungating tumours
• malignant ulcers
• infiltrating carcinoma

Fungating tumours are usually polypoid and may grow to be very large. They tend to have a better prognosis than the other morphological types.

Mucosal ulcers are broad-based tumours with a necrotic centre. They are broader than most peptic ulcers except the benign giant ulcer seen in the elderly. The edge of the tumour is heaped-up and indurated. Also, there is none of the surrounding puckered mucosa that is characteristic of peptic ulcers.

Infiltrating carcinomas spread widely beneath the mucosa and invade the muscular layer. As a result, the stomach wall may become thickened and rigid and the capacity of the stomach reduced. This is a so-called 'leather bottle' stomach and carries a very poor prognosis.

In most gastric carcinomas the cells are well differentiated. The exception is in the case of infiltrating carcinomas where large mucin droplets displace the nuclei laterally producing the so-called 'signet ring appearance'.

There are 2 systems most often used to describe how gastric adenocarcinomas look and develop; the Lauren classification (1) and the World Health Organisation (WHO) classificatioin (2)

• the Lauren classification divides adenocarcinomas into 2 main groups, solid tumours known as an intestinal type accounting for most stomach cancer diagnoses and diffuse type which are poorly differentiated tumour cells scattered throughout the stomach found in 1% to 3% of cases (1). Some people can have a mix of intestinal and diffuse types of tumour
• the WHO classification separates stomach cancers by their morphology; tubular adenocarcinoma is made up of branching tubules; papillary adenocarcinoma comprises finger like tumours growing out of the stomach wall; mucinous adenocarcinoma has a lot of mucin surrounding the cancer cells; poorly cohesive carcinomas are clumps of tumour cells and mixed carcinoma can be a mix of any of the 5 types (2)

Gastric adenocarcinomas are usually classified as cardia and non-cardia according to their anatomical site

• non-cardia cancer, also known as distal stomach cancer occurs in the lower portion of the stomach whereas, cardia stomach cancers occur at the top of the stomach, close to where the stomach joins the oesophagus (1)
• despite the overall decline in gastric adenocarcinoma there is evidence that the incidence of cardia cancers in many countries including the UK, is increasing (1)
• there has been a particular focus of some studies on the link between obesity and development of gastric adenocarcinoma in the stomach cardia adjacent to the oesophagus (1)
• there is a suggestion that some gastric adenocarcinomas of the cardia have a similar aetiology to oesophageal adenocarcinoma occurring near the junction of the oesophagus and the stomach. Increasing obesity is thought to be responsible for an increase in gastro-oesophageal reflux disease; a risk factor for oesophageal adenocarcinoma and this has also been implicated in the rise of stomach cardia cancers (1)

Reference:

• Mukaisho K, Nakayama T, Hagiwara T, Hattori T and Sugihara H. Two distinct etiologies of gastric cardia adenocarcinoma: interactions among pH, Helicobacter pylori, and bile acids. Front. Microbiol. 2015: 6:412.
• Bosman FT, Carneiro F, Hruban RH, Theise ND. (2010). WHO Classification of Tumours of the Digestive System. (4th Edition). Lyon: International Agency for Research on Cancer (IARC).