**2.4. Ming classification (established 1997)**

According to the infiltration zone, tumours with expanding, pushing border and tumours with infiltrating margins have separated. Types and architecture of tumour cells are not included.

**1.** Expanding type

cohesive tumour cells can be misinterpreted as lymphatic blasts. Typically, this subtype is EBV-related and it is easy to detect EBV-RNA using *in-situ*-test like EBER. Furthermore, carcinoma cells are often immunohistochemically strong PD-L1 positive. Nevertheless, not all EBV-related adenocarcinomas show the typical medullary morphological features. Some carcinomas of this subtype are microsatellite-instable easy and cost-effective detectable using immunohistochemistry for MLH1 (MSH2, MLH6 and PMS2). The loss of one (or more) of these DNA-repair proteins in tumour cell nuclei is in keeping with microsatellite-instability.

A pure gastric squamous cell carcinoma is very rare and is suspicious for a metastasis.

Cohesive tumour cells form tubular, papillary or solid structures. The tumour typically shows well-demarcated pushing borders and it is associated with chronic gastritis (usually w Hp-infection) including intestinal metaplasia and pre-cancerogenous epithelial lesions like flat intraepithelial neoplasia/dysplasia. Abundant intracytoplasmic mucin production is not

Poorly or non-cohesive tumour cells include signet-ring cells. The tumour typically shows infiltrating margins. Usually intestinal metaplasia of the gastric mucosa or classic dysplasia is absent. Probably a signet-ring cell carcinoma *in situ* develops from the proliferative foveolar

According to the degree of tubular differentiation and the amount of intracellular mucin, this

**1.** Tubular differentiation, mainly (just a few tumour cells with intracellular mucin allowed)

**3.** Minor components of both: few tubular differentiations and few intracellular mucin

**2.** Tubular differentiation accompanied by abundant intracellular mucin

**4.** Abundant intracellular mucin and no/very few tubular differentiation

Sometimes a mixed adeno-squamous cell carcinoma can be seen.

**2.2. Classification according to Lauren (established 1965)**

zone and directly invades into the lamina propria.

Mix of intestinal type and diffuse type tumour cells.

**2.3. Goseki classification (established 1992)**

classification separates four subtypes.

*2.1.6.2. Squamous cell carcinoma*

*2.2.1. Intestinal type*

a feature.

272 Gastric Cancer

*2.2.2. Diffuse type*

*2.2.3. Indeterminate type*

**2.** Infiltrating type
