Stomach cancer pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Parminder Dhingra, M.D. [2]

Stomach cancer Microchapters
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Overview
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Differentiating Stomach Cancer from other Diseases
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Overview

The pathophysiology of stomach cancer depends on histologic subtypes.

Gross pathology

Type	Description
Type 0	(superficial) Typical of T1 tumors.
Type 1	(mass) Polypoid tumors sharply demarcated from the surrounding mucosa.
Type 2	(ulcerative) Ulcerated tumors with raised margins surrounded by a thickened gastric wall with clear margins.
Type 3	(infiltrative ulcerative) Ulcerated tumors with raised margins, surrounded by a thickened gastric wall without clear margins
Type 4	(diffuse infiltrative) Tumors without marked ulceration or raised margins, the gastric wall is thickened and indurated and the margin is unclear.
Type 5	(unclassifiable) Tumors that cannot be classified into any of the above types.

Histopathology

• Gastric adenocarcinoma is a malignant epithelial tumor, originating from glandular epithelium of the gastric mucosa. It invades the gastric wall, infiltrating the muscularis mucosae, the submucosa and hence the muscularis propria. Histologically, there are two major types of gastric cancer (Lauren classification): intestinal type and diffuse type.
  • Intestinal type adenocarcinoma: Tumor cells describe irregular tubular structures, harboring pluristratification, multiple lumens, and reduced stroma ("back to back" aspect). Often, it associates intestinal metaplasia in neighboring mucosa. Depending on glandular architecture, cellular pleomorphism and mucosecretion, adenocarcinoma may present 3 degrees of differentiation: well, moderate and poorly differentiated.
  • Diffuse type adenocarcinoma (mucinous, colloid): tumor cells are discohesive and secrete mucus which is delivered in the interstitium producing large pools of mucus/colloid (optically "empty" spaces). It is poorly differentiated. If the mucus remains inside the tumor cell, it pushes the nucleus at the periphery - "signet-ring cell".

World Health Organization histological classification of gastric tumors:

Types	Histological features
Epithelial tumors	Adenoma Carcinoma Adenocarcinoma Intestinal type Diffuse type Papillary adenocarcinoma Tubular adenocarcinoma Mucinous adenocarcinoma Signet-ring cell carcinoma Adenosquamous carcinoma Squamous cell carcinoma Small cell carcinoma Undifferentiated carcinoma Carcinoid (well differentiated endocrine neoplasm)
Non-epithelial tumors	Leiomyoma Schwannoma Granular cell tumour Glomus tumour Leiomyosarcoma GI stromal tumour Benign Uncertain malignant potential Malignant Kaposi sarcoma
Malignant lymphomas	Marginal zone B-cell lymphoma of MALT-type Mantle cell lymphoma Diffuse large B-cell lymphoma

Japanese histological classification of gastric tumors:

	Benign epithelial tumor Adenoma Malignant epithelial tumor Common type Papillary adenocarcinoma Tubular adenocarcinoma Well-differentiated Moderately differentiated Poorly differentiated adenocarcinoma Solid type Non-solid type Signet-ring cell carcinoma Mucinous adenocarcinoma
Special types	Carcinoid tumor Endocrine carcinoma Carcinoma with lymphoid stroma Hepatoid adenocarcinoma Adenosquamous carcinoma Squamous cell carcinoma Undifferentiated carcinoma
Miscellaneous carcinoma	Non-epithelial tumor Gastrointestinal stromal tumor (GIST) Smooth muscle tumor Neurogenic tumor Miscellaneous non-epithelial tumors Lymphoma B-cell lymphoma MALT (mucosa-associated lymphoid tissue) lymphoma Follicular lymphoma Mantle cell lymphoma Diffuse large B-cell lymphoma Other B-cell lymphomas T-cell lymphoma Other lymphomas Metastatic tumor Tumor-like lesion Hyperplastic polyp Fundic gland polyp Heterotopic submucosal gland Heterotopic pancreas Inflammatory fibroid polyp Gastrointestinal polyposis Familial polyposis coli, Peutz–Jeghers syndrome