The stomach is divided into the cardia,
The stomach wall is made up of several layers of tissue:
- Mucosa : the mucous membrane layer of the stomach which contains the many glands and the gastric pits.
- Submucosa : A layer of connective tissue that has large blood vessels,
nerve cells and fibres,
and glands that secrete digestive hormones.
- Muscularis propria (or muscularis externa) : The main muscle of the stomach,
and is made up of 3 layers of muscle.
- Serosa : The fibrous membrane covering the outside of the stomach.
Fig. 2: Layers of the stomach wall
Determination of Mass Origin in the GI Wall with CT
CT imaging are of limited value due to their inability to allow differentiation of GI wall layers.
CT can be helpful in characterizing a tumor by using contrast enhancement,
in determining the site of origin of a mass lesion,
in delineating the full extent of a tumor,
and in detecting local invasion and distant metastases.
CT may be helpful in distinguishing between epithelial and subepithelial masses.
Subepithelial masses or masslike lesions have varying degrees of enhancement.
Identification of prominent feeding blood vessels adjacent to tumor foci may help improve the detection of small hypervascular subepithelial masses.
At contrast-enhanced CT,
the normal GI wall demonstrates layered enhancement(Fig.2).
An inner mucosal layer with marked enhancement,
a middle submucosal layer with lower attenuation,
and an outer muscular-serosal layer with moderate enhancement.
This layered appearance is more commonly seen during the arterial phase.
Intramural subepithelial masses appear at CT as well-defined smooth-surface masses with intraluminal or extraluminal growth; the overlying mucosal layer is generally intact,
with the exception of the focal ulcerated area.
The identification of mucosal changes such as mucosal ulceration,
and irregularity at CT may be important in differentiating epithelial masses from subepithelial masses.
The first choice for examining submucosal lesions in the upper GI tract.
Important application of EUS is to stage GI malignancy,
also to differentiate the type of submucosal tumors by their original layers.
The sensitivity of cytological samples achieved through EUS-FNA has been reported to be 88-91% and the specificity was 100% for the diagnosis of malignant lesions.
Standard EUS is able to show 5 layers of the gastrointestinal wall of alternating hyperechoic and hypoechoic layers,
with higherfrequency probes,
7 or more layers can be seen(Fig.
Fig. 3: The layer structure of the gastrointestinal tract by the endoscopic ultrasonography
Gastric submucosal tumors
A variety of neoplastic and nonneoplastic condition arising from deeper layers of the wall of the GI tract,
the overlying mucosa is not involved.
In the case of CT,
MRI and EUS,
the term submucosal tumor (SMT) is really a misnomer.
Because lesions in this category do not necessarily arise or confine themselves to the submucosa.
Any growth underneath the mucosa of the GI tract whose etiology cannot readily be determined by lumenal diagnostic endoscopy or barium radiography is called an SMT.
The overlying mucosa usually appears smooth and normal at endoscopy.
The majority of subepithelial masses do not cause symptoms and are discovered incidentally during endoscopic or radiologic examinations.
Large submucosal neoplasms may outgrow their blood supply,
ulcerate through the mucosa,
and present with GI bleeding.
Firm subepithelial masses may also present with obstructive symptoms,
especially if they are located near the cardia,
or the ileocecal valve.
Pain and weight loss,
often associated with very large submucosal GI stromal tumors,
are symptoms that suggest malignancy.
Gastric submucosal tumors smaller than 3 cm are generally considered benign tumors.
- Interstitial Cell of Cajal or it’s precursor
- express C-kit(95%) or CD34(5%)
- 2-5% of all gastric tumors
- 10-30% are malignant
- 60-70% occur in the stomach
- Higher incidence in middle age and eldery individuals
- The body is the most common site,
followed by the fundus and then the antrum
- Epigastric pain,
- Metastatic disease(Liver,
- May have areas of necrosis,
ulceration or fistulization to the gastrointestinal lumen(Fig.5)
- May invade adjacent organs in an advanced stage
- Small GISTs are more homogeneous and may be intramural or endoluminal
- After Ⅳ contrast
- Vessels may be seen crossing the tumor
- a hypoechoic mass with a homogeneous echo texture that is contiguous with the muscularis propria.
Fig. 4: GIST
a:Axial contrast-enhanced CT scan shows a round and homogeneous low-density mass in the fundus of the stomach (arrow).
b:An EUS shows a well defined hypoechoic submucosal mass
c:Histologic images. Bland spindle cells forming whorls and short intersecting fascicles. The tumor cells was positive for c-kit.
d:Endoscopy shows an elevated submucosal mass covered with normal mucosa in the body of the stomach.
Fig. 5: Growth patterns of intramural masses.
a-b:Axial contrast-enhanced CT image shows an GIST with focal ulceration (arrow).
c-d:Giant GISTs often demonstrate an exophytic pattern of growth.
- Smooth muscle in the muscularis propia or muscularis
- Rare in the stomach (higher incidence in the esophagus)
- Adult age
- Usually asymptomatic
- Epigastric pain,
- Round or oval solid hypoattenuating homogeneous mass
- Well defined margins
- May be intramural or exhibit intra or extraluminal growth
- May ulcerate or present areas of calcification
- Arising from the muscularis propia of the muscularis mucosae
Fig. 6: Leiomyoma
a:Axial contrast-enhanced CT image shows a leiomyoma(arrow) in the body of the stomach, with intact enhancing mucosa.
b:An EUS image of a gastric leiomyoma depicted as a hypoechoic solid mass in body of stomach.
c:Leiomyoma shows bundles of elongate cells with eosinophilic cytoplasm and oblong nuclei. The tumor cells was positive for α-smooth muscle actin (α-SMA).
d:Endoscopic image shows that the mass has smooth, overlying mucosa.
- Proliferation of mature adipose tissue enciosed in a fibrous capsule
- 3% of all benign gastric tumors
- 5% of all gastrointestinal lipomas
- May present with areas of ulceration on cystic degeneration
- 75% occus as solitary lesions of the antrum
- When >4cm,
may produce gastrointestinal bleeding,
abdominal pain or obstruction due to ulceration or intussusception
- Well defined mass with homogeneous fat attenuation
- After Ⅳ contrast:No significant enhancement
- Hyperechogenic mass with regular contours developed in the submucosal layer
Fig. 7: Lipoma
a:Lipomas present as well-defined and homogenous fat-density lesions.
b:EUS image showing a hyperechoic, homogeneous mass arising from the third sonographic layer of the gastric wall.
c:Endoscopy shows an elevated submucosal mass covered with normal mucosa in the gastric antrum.
- Pancreatic tissue remnants,
with all pancreatic tissue components
- Present in 0.6 to 14% of autopsies
- Present in 1 in every 500 gastric surgical speciments
- Higher incidence in male,
40-60 years old
- Antrum or greater curvature,
less than 6cm from the pylorus in 85-95%
- Epigastric pain,
- Oval or rounded,
well-defined mass measuring 1 to 3 cm
- Smooth or lobulated margins
- Central umbilication(20-40%)
- May present with cystic areas
- After Ⅳ contrast:Intense enhancement
- Hypoechoic or mixed echogenicity (ductal structures may be present)
Fig. 8: Heterotopic pancreas
a:Axial contrast-enhanced CT image shows a small oval intramural gastric mass (arrow) with a predominantly endoluminal growth pattern.
b:EUS image shows the mass (arrow) disrupting the hyperechoic submucosal layer of the gastric wall.
c:Corresponding photomicrograph shows pancreatic acini within the submucosa. (H&E, ×200.)
d:Endoscopic image shows a submucosal mass (arrow) .
- Arising from the Schwann cells of the neural plexus of the gastrointestinal wall
- 5～10% of benign gastric tumors
- Higher incidence in females,
40-60 years old
- Gastric body
- Demonstrating an exopytic or intramural pattern of growth
- Occur most frequently in the third to fifth decades of life
- abdominal pain or gastrointestinal bleeding
- Low attenuation on unenhanced CT images
- No or minimal enhancement during the arterial phase
- Delayed enhancement during the equilibrium phase
- Hypoechoic internal echoes with a marginal halo and without internal echogenic foci
Fig. 9: Schwannoma
a:Axial contrast-enhanced CT shows a well-defined, rounded, mural mass with homogeneous attenuation in the body of stomach.
b:EUS image shows heterogeneous with an echogenicity lower than that of the surrounding normal proper muscle layer.
c:Corresponding photomicrograph shows spindle cell proliferation with interlacing and palisading patterns.
d:Endoscopic image shows that the mass has smooth, overlying mucosa.
- Originate from enterochromaffin-like cells (Kulchitsky cells) in the gastric mucosa
- Accounting for 1.8% of all gastric malignancies
- The small bowel is the most common location,
followed by the rectum,
chronic atrophic gastritis(type 1,2)
- Abdominal pain,
- Type 1 : multiple small hyperenhancing masses are seen,
usually less than 1 cm and almost always less than 2cm
- Type 2 : The gastric wall is typically thickened,
and there are typically multiple masses present but of variable size.
- Generally homogeneous,
and mildly hypoechoic
- Usually present in the first,
and third layer
Fig. 10: Carcinoid Tumor
a:Axial contrast-enhanced CT image shows type 1 gastric carcinoid, with enhancing polypoid lesions.
b:EUS image revealing GI stromal tumor, deriving from the third layer of the gastric wall.
c:At greater magnification, the nests of carcinoid tumor have a typical endocrine appearance with small round cells having small round nuclei and pink to pale blue cytoplasm. The tumor cells was positive for Chromogranin A (CGA).
d:Endoscopic image shows that the mass has smooth, overlying mucosa in the body of stomach.
- Vascular tumors that originate from glomus bodies
- 2% of all benign gastric tumors
- They appear as a solitary,
intramural subepithelial mass in the stomach,
particularly the antrum
- They are usually smaller than 3 cm in diameter.
or they can present with epigastric discomfort,
- Nonenhanced CT reveals a well-defined subepithelial mass with homogeneous attenuation located in the antrum.
- At dynamic contrast-enhanced CT,
the tumor demonstrates strong peripheral nodular or homogeneous enhancement in the arterial and portal phases and prolonged enhancement in the delayed.
- EUS shows a hypoechoic,
well-circumscribed tumor located in the 3rd and or 4th sonographic layer.
- However EUS morphologic findings are insufficient for diagnosis and EUS-FNA is required.
Fig. 11: Glomus tumor
a:Axial contrast-enhanced CT image shows well-defined subepithelial mass with homogeneous strong enhancement in the gastric antrum.
b:EUS image shows a well-defined mass in the third and fourth layers of the gastric wall with a hypoechoic pattern.
c:Greater magnification of are sected specimen shows a relatively uniform population of small cells with oval nuclei.
d:Immuno-histochemical staining of the tumor cells was positive for α-smooth muscle actin.
- Primary gastric lymphomas are confined to the stomach and regional lymph nodes and are predominantly non-Hodgkin lymphomas of B-cell origin.
- MALT Lymphoma is a distinct type of extranodal lymphoma that is characterized by a relatively indolent clinical course.
- MALT lymphomas comprise 50% of all gastric lymphomas
- Ethnicity: no significant differences
- Gender: no significant differences
- Age: median age 65,
but can occur at any age
- Lymphomas may involve any portion of the stomach.
- Most cases involve the antrum and body.
- Symptoms of lymphoma are nonspecific,
and may mimic peptic.
- Ulcer disease or gastritis.Lymph node involvement is rare.
- Wall thickening of 1 cm,
diffuse infiltration of 50% of the wall
- Circumferential involvement of most of the stomach
- Segmental infiltration of the stomach
- Homogeneous wall thickening with preservation of the overlying rugae
- Localized polypoid lesions with ulcers or perforations
- Presence of lymph nodes on either side of the mesenteric vessels (the sandwich sign)
- A very accurate technique to assess T- and N-staging of primary gastric lymphoma.
- Lymphomas tend to show mainly a horizontal extension
- EUS can differentiate between lymphomas and carcinomas in early stages,
but in advanced stages both have similar appearances.
Fig. 12: Malignant lymphoma
a:Axial contrast-enhanced CT image shows large areas of gastric wall thickening.
b:Endoscopic image shows giant gastric folds and gastritis-like lesions with nodular aspect and erosions.
c:Histologic images. The tumor cells was positive for CD3 and CD20.
- The majority of lesions are hematogenous metastases from malignant melanoma or carcinoma of the breast or lung.
metastases from ovarian,
kidney and hepatic carcinomas can occur.
- They are found at autopsy in less than 2% of patients who die of carcinoma.
- Usually affects the middle-aged and elderly population.
- Metastasis may involve any portion of the stomach.
- There may be a predilection for the middle and upper thirds of the stomach.
or they can present with weight loss,
melaena or palpable mass.
- CT imaging findings depends mainly on the histologic characteristics of the primary or secondary lesions,
such as the degree of vascularity relative to the growth rate.
- EUS examination of most metastatic lesions will show a hypoechoic lesion that can be in any layer of the gastric wall.
- EUS morphologic findings are insufficient for diagnosis and EUS-FNA is required.
Fig. 13: Metastasis
a:Axial contrast-enhanced CT image shows a well defined, highly enhancing submucosal mass with central ulceration in the body of stomach.
b:Endoscopic image shows a well defined submucosal mass with central ulceration.
c:Metastasis of sigmoid colon cancer. The tumor cells was CK7 positivity and CK20 positivity.
Differential diagnosis between epithelial and submucosal lesions as seen as on CT
- Acute angle,
- thickened mucosal layer
- Endophytic growth
- Obtuse angle,
- Normal thickness mucosal layer(although it may ulcerate)
- Esophytic growth(there are many exceptions)
Fig. 14: Differential diagnosis between epithelial and submucosal lesions as seen as on CT