(1)
Department of Pathology, Sinai Hospital of Baltimore Pathology, Baltimore, MD, USA
Keywords
HelicobacterGastritisOxynticAntralAtrophyLymphomaPolypsCeliac diseaseGISTStomach
The stomach is composed of several anatomic zones. Moving proximal to distal, like a piece of food, you pass (1) the gastroesophageal junction, (2) the cardia, (3) the fundus and body, (4) the antrum, and (5) the pylorus (Table 7.1 and Figure 7.1). For the pathologist, there are essentially two types of mucosa in the stomach (Figure 7.2): antral (mucinous or protective) and oxyntic (secretory). The entire stomach epithelium is composed of pits (invaginations from the surface) and glands (deep to the pits). The surface and pits are lined by columnar mucinous epithelium (called foveolar type) which stains bright pink with PAS/AB. The regions of the stomach are divided by the type of underlying glands:
Table 7.1.
Anatomic zones of the stomach.
Histology | Endocrine cells | Common pathology | |
|---|---|---|---|
Esophagus | Squamous | None | Reflux esophagitis |
Eosinophilic esophagitis | |||
Barrett esophagus | |||
Cardia | Mucinous (antral) | Reflux carditis | |
H. pylori gastritis | |||
Body and fundus | Oxyntic | Enterochromaffin-like | Autoimmune gastritis |
Antrum | Mucinous (antral) | Gastrin, somatostatin, enterochromaffin | H. pylori gastritis |
Chemical gastritis | |||
Pylorus | Antral to duodenal | Chemical gastritis |
Figure 7.1.
Localization of anatomic regions within the stomach: (1) the gastroesophageal junction, (2) the cardia, (3) the fundus and body, (4) the antrum, and (5) the pylorus. Antral-type (mucinous) mucosa is seen in the cardia, antrum, and pylorus.
Figure 7.2.
Antral and oxyntic mucosa. (a) Oxyntic mucosa is relatively thick, with most of the mucosa occupied by secretory cells (arrow), the parietal and chief cells. The surface is composed of mucinous foveolar epithelium. (b) Antral mucosa is thinner, and the glands are mucinous instead of secretory (arrow). However, the surface is still composed of foveolar epithelium (arrowhead).
Antral mucosa (found at the borders of the stomach—the cardia, antrum, and pyloric regions): the glands are loosely packed and mucinous and occupy about half of the epithelial thickness (meaning the other half are the pits from the surface).
Oxyntic mucosa (found in the digestive regions of the stomach—the fundus and body): the glands are tightly packed, contain granular parietal (pink, acid-secreting) and chief (purple, enzyme-secreting) cells, and occupy three fourths of the mucosal thickness.
Transitional mucosa: An overlap zone where features of both antral and oxyntic are present.
It is important to note what kind of epithelium is present in the biopsy tissue because there are certain processes that differentially affect mucosal types; clarifying the type of epithelium involved may change the differential.
Endocrine cells occur singly in the glands. In the body, they are mainly enterochromaffin-like (ECL) cells, while in the antrum they are mixed gastrin-, enterochromaffin-, and somatostatin-producing cells. A chromogranin stain highlights all endocrine cells. A gastrin stain should be positive only in the antrum.
The Approach to the Biopsy
Survey the glandular epithelium at low power:
Note what kind of mucosa you have and whether it correlates with what the endoscopist thought.
Assess the color of the biopsy specimen. A healthy stomach is a fairly pale pink, overall. If your general impression is blue, this probably indicates inflammation in the stroma, such as in gastritis (Figure 7.3). If your impression is that of a pink stroma with unusually dark and distinct glands, you may be looking at chemical gastritis.
Figure 7.3.
Helicobacter pylori gastritis , antrum. In this disease, the low-power impression is that of a “blue” biopsy due to the dense inflammatory infiltrate in the lamina propria (arrow). There are lymphocytes, plasma cells, and neutrophils. Neutrophils in the glandular or surface epithelium (arrowheads) indicate an active component to this gastritis. H. pylori organisms are pictured in Chapter 3.
Look for intestinal metaplasia, or goblet cells, a marker of chronic irritation in the stomach. Goblet cells are usually visible from low power, especially on a PAS/AB stain (as indigo-blue, bulbous cells). Remember that true goblet cells are usually interspersed among nonmucinous pink cells (absorptive). A row of back-to-back tall mucinous cells, even if blue on PAS/AB, is unlikely to be actual intestinal metaplasia.
Look for areas of exudate, neutrophils, debris, and ragged-looking glands that indicate an erosion or ulcer.
On higher power, assess the inflammation:
A few lymphocytes, plasma cells, and rare eosinophils are okay in the lamina propria of the stomach, especially in the antrum, where there is more space between glands. However, back-to-back lymphocytes and plasma cells pushing aside or crowding the glands indicate chronic gastritis .
Neutrophils in the epithelium indicate activity (by convention, active inflammation is used instead of acute). If you have only mononuclear cells, you have inactive chronic gastritis , but if there are any neutrophils embedded in the surface or glandular epithelium, you have active chronic gastritis.
Eosinophils can be a normal component, but dense sheets of eosinophils in the lamina propria may indicate allergic or eosinophilic gastritis.
How many lymphocytes does it take to diagnose lymphoma? The answer is a lot. See the section on lymphoma, below.
How about lymphocytes in the surface epithelium? Extensive intraepithelial lymphocytes in the stomach may be seen in patients who also have celiac disease and/or lymphocytic gastritis/colitis.
Active chronic gastritis and lymphoid follicles are usually indicative of Helicobacter pylori infection. The tiny rods are visible on H&E stain (see Chapter 3) but are better seen on Diff-Quik or Giemsa (immunohistochemistry for H. pylori is helpful if organisms are sparse). They should be visible at 40× as tiny discrete seagull-shaped rods in the pit lumens or on the surface, mainly in the antrum, unless there is intestinal metaplasia, a hostile mucosa for these bugs. If you have no significant inflammation, do not work too hard looking for H. pylori.
Another cause of unexplained active or inactive chronic gastritis is inflammatory bowel disease, especially Crohn’s disease (see Chapter 8). Think of Crohn’s if you find granulomas in the stomach, or an unexplained active chronic gastritis in a child.
Foveolar Hyperplasia and Chemical Gastritis
Especially in the antrum, the stomach is vulnerable to bile reflux. Bile and other sources of chemical irritation, such as nonsteroidal anti-inflammatory drugs, cause a process called foveolar hyperplasia . The surface mucin cells proliferate, giving the surface a papillary appearance and the pits a corkscrew profile. The mucinous cells lose mucin, and the cytoplasm becomes more dark or opaque; the nuclei also may become hyperchromatic, adding to the dark look (Figure 7.4). Smooth muscle fibers proliferate and can be seen stranding up between the pits. Inflammation in the stroma is not a prominent feature, so the lamina propria is often fairly pale, even edematous. This appearance is called chemical gastritis or chemical gastropathy, and it is very common.
