*2.1.5. Mixed adenocarcinoma*

*2.1.4. Signet-ring cell and other poorly cohesive adenocarcinoma*

Sometimes signet-ring cells can form lace-like glands.

gates of few cells (**Figure 2D**).

**Table 1.** Classification systems of adenocarcinoma.

Mucinous adenocarcinoma

And other poorly cohesive

Adenosquamous carcinoma Squamous cell carcinoma Hepatoid adenocarcinoma Carcinoma with lymphoid

Mixed carcinoma Indeterminate-type

carcinoma

270 Gastric Cancer

stroma

carcinoma

Endodermal sinus tumour Embryonal carcinoma Pure gastric yolk sac tumour Oncocytic adenocarcinoma

to the other classifications. \*MSI, microsatellite instable.

Choriocarcinoma Carcinosarcoma Parietal cell carcinoma Malignant rhabdoid tumour Mucoepidermoid carcinoma Paneth cell carcinoma Undifferentiated carcinoma Mixed adeno-neuroendocrine

Non-cohesive, isolated single tumour cells or carcinoma cells arranged in only small aggre-

*Notes*: The correlation between the different classification systems is relative. The Ming classification cannot be assigned

**WHO (2010) Lauren (1965) Goseki (1992) Ming (1992) Molecular (2014)** Papillary adenocarcinoma Intestinal type (Expanding type) Chromosomal instable, MSI\* Tubular adenocarcinoma Type 1 (type 2,

Signet-ring cell carcinoma Diffuse type type 4 Genomic stable

type 3)

(Infiltrating type)

EBV-related; MSI\*

Signet-ring cell carcinoma is composed of more than 50% signet-ring cells. The classic form of signet-ring cells is usually a single cell and has a central droplet of cytoplasmic mucin (optically clear in HE-staining). The atypical, hyperchromatic nucleus is eccentrically placed. As described above, gastric carcinoma is highly heterogeneous (from the morphological as well as molecular point of view). The 'mixed' subtype is composed of different cohesive or poorly cohesive tumour components of the main four subtypes described above (for example tubular and signet-ring cell components). It is recommended to describe any histological component.

#### *2.1.6. Rare carcinoma variants (to see all: compare* **Table 1***)*
