Keywords
duodenum - lymphoma - stomach
Introduction
Neoplasms of the stomach are classified into two large categories on the basis of
the cell of origin: epithelial and nonepithelial.[1]
[2] The vast majority of both benign and malignant tumors of the stomach are of epithelial
origin, with mesenchymal and neuroendocrine tumors (NET) being much less common. The
epithelial tumors arise from the mucosa while the nonepithelial tumors arise from
the submucosa, muscularis propria, or serosa.
The nonepithelial or intramural tumors of stomach include gastrointestinal (GI) stromal
tumors (GISTs), leiomyomas, schwannoma, granular cell tumors, glomus tumor, NET, leiomyosarcoma,
Kaposi sarcoma, lymphoma, and others.[1] The duodenum is a common site for small bowel tumors accounting for 20% of these
neoplasms. They are classified into benign and malignant categories. The benign tumors
seen involving the duodenum are GISTs, lipomas, and adenomas, whereas the malignant
primary neoplasms include adenocarcinomas that are epithelial in origin while the
nonepithelial or intramural tumors include lymphoma, paraganglioma, and secondary
tumors.[3]
Patients with mesenchymal tumors can be asymptomatic independent of the location,
if large enough may cause gastric hemorrhage and present with vague symptoms like
abdominal pain or mass. Very rarely they cause obstruction or intussusception.
Mesenchymal tumors are often well circumscribed, with intact overlying mucosa except
in larger tumors (>2 cm in size), the overlying mucosa can be ulcerated due to necrosis.
They grow in exophytic, endoluminal, or mixed pattern giving dumbbell-shaped appearance.
Because of various overlapping features, differentiating between these tumors can
be challenging. However, the combination of features like margins, location, growth
pattern, and enhancement may help in narrowing down the differential diagnosis. In
this article, we review the radiological features of the mesenchymal and lymphoproliferative
tumors of stomach and duodenum ([Table 1]).
Table 1
Imaging features of tumors
|
Name of the tumor
|
Appearance
|
Arterial enhancement
|
Venous enhancement
|
Other relevant finding
|
|
Abbreviation: GIST, gastrointestinal stromal tumor.
|
|
GIST
|
Larger lesions may be exophytic, heterogeneously enhancing with necrosis
Smaller lesions may enhance uniformly
|
May be present, particularly in metastases
|
Increased enhancement
|
CD117 and CD34 positive
May metastasize
|
|
Leiomyoma
|
Homogeneous, low-attenuation masses with an endoluminal growth pattern
|
None
|
Homogenous enhancement
|
Positive for desmin
|
|
Leiomyosarcoma
|
Large, aggressive tumors with heterogeneous enhancement and areas of necrosis
|
|
Enhancement with necrotic areas
|
Invasion of adjacent organs
|
|
Lipoma
|
endoluminal, fat density (−70 to −120 HU), arising in the submucosa
|
None
|
None
|
May be pliable or deform during compression
|
|
Neurogenic tumors
|
Well-defined, intramural, or exophytic lesions
|
|
None or minimal enhancement
|
Features of neurofibromatosis
|
|
Glomus tumors
|
Solitary, most common in gastric antrum
|
Dense arterial enhancement
|
Delayed filling similar to a hemangioma
|
|
|
Kaposi’s sarcoma
|
Polypoid submucosal masses 0.5 to 3 cm in diameter and irregular fold thickening
Target lesions on double contrast examination
|
|
Usually homogenous enhancement
|
Hyperattenuating lymphadenopathies
|
|
Neuroendocrine tumors (carcinoid)
|
Type 1: multiple polyps of less than 2 cm in diameter
Type 2: multiple masses in the setting of diffuse gastric wall thickening
Type 3: usually solitary submucosal tumors
|
Hyperenhancing liver metastasis
|
Primary lesion shows venous enhancement
|
Primary lesion shows uptake on Octreotide scans (Ga-68 DOTATATE)
Type 1 associated with autoimmune gastritis and type 2 are associated with MEN-1
|
|
Hamartomas
|
Smooth intraluminal lesions
|
|
Homogenous enhancement
|
Genetic testing for Peutz–Jeghers syndrome
|
|
Lymphoma
|
Marked gastric wall thickening, multiple enlarged enhancing lymph nodes
|
|
Homogenous enhancement
|
Other organ involvement
Lymph nodes
Aneurysmal dilatation
|
Imaging Technique
Intramural tumors are quite often diagnosed incidentally. However, whenever dedicated
evaluation of stomach and duodenum is required, adequate distention with sufficient
quantities of radiopaque oral contrast should be achieved to differentiate between
small tumors and thickened gastric rugae. Bicarbonate granules can also be used which
distend stomach and duodenum through release of CO2.[3] On barium meal examination, these intramural tumors reveal intact and smooth mucosal
surface forming obtuse angle with the stomach wall and as a filling defect. A CT scan
is routinely performed in these patients as the fluoroscopy has limitations in evaluation
of extraluminal extension of these masses.
On CT evaluation, the gastric distention is usually achieved by using oral contrast.
A negative oral contrast (like water) is used if mucosal enhancement is to be evaluated
([Fig. 1]). During CT examinations, up to 200 mL of enteral contrast should be administered
just prior to scanning to outline and distend the stomach and duodenum. The mucosal
enhancement can be appreciated as a prominent linear enhancement in arterial phase
of imaging. In later phases, the gastric wall enhances as a single layer. Hence, a
dual phase imaging technique (arterial and portal venous phases) is helpful which
also helps in detection of hypervascular lesions or metastatic lesions (particularly
GIST or NET).[4]
[5]
Fig. 1 Gastric computed tomography. (A) Coronal view performed with carbon dioxide causing negative contrast (arrow). (B) With water providing neutral contrast within the gastric lumen (arrow).
Gastrointestinal Stromal Tumors
Gastrointestinal Stromal Tumors
The most common GI mesenchymal neoplasms are GIST.[6] The term GIST is now used for a specific group of tumors comprising the majority
of all GI mesenchymal tumors. GISTs differ from smooth muscle neoplasms in that they
are derived from a precursor of the intestinal pacemaker cells of Cajal rather than
from smooth muscle cells.[7]
[8]
[9] They are most common in the stomach (60–70%), followed by small intestine (20–30%),
colorectum, and esophagus (together < 10%).[2] They can be found in extravisceral locations as well like mesentery, omentum, and
retroperitoneum. In the stomach, most common location is body followed by the fundus
and then antrum.
GIST predominantly occurs in middle-aged and older persons (5th to 7th decade), with
no significant difference in distribution between males and females. The symptoms,
which depend on tumor size and location, are usually nonspecific. The commonest presentation
of GIST is bleeding secondary to mucosal erosion by the tumor.[10]
GISTs are characterized by immunoreactivity for c-KIT (CD117), a growth factor receptor
tyrosine kinase that is normally expressed on hematopoietic stem cells, mast cells,
melanocytes, and the myenteric plexus of the normal adult GI tract. Approximately
70 to 80% of GISTs are also positive for CD34.2 Evaluation of malignancy of GISTs
is based on mitotic count, tumor size, and extragastrointestinal spread. Tumors with
mitotic counts higher than 5/10 high power fields or larger than 10 cm have a significant
risk for recurrence and metastasis, and are considered histologically malignant.[9] Histologic characteristics of GISTs usually consist of interlacing whorls of spindle-shaped
cells with eosinophilic cytoplasm and elongated nuclei, although tumors completely
composed of ovoid cells are not uncommon. Immunoreactivity to c-KIT or DOG1 confirms
the diagnosis.
The CT features of GISTs vary greatly, depending on the size and aggressiveness of
the tumor and the time of presentation during the course of the disease. Primary GISTs
are typically large, hypervascular, and enhancing masses on contrast enhanced CT scans,
and they are often heterogeneous because of necrosis, hemorrhage, or cystic degeneration
at the time of presentation[5]
[11] ([Fig. 2]). Ulceration and fistulization to the GI lumen are also common features of GISTs.
Often, tumor vessels can be seen within the tumors. The masses usually displace adjacent
organs and vessels; however, direct invasion of the adjacent structures may be rarely
seen with advanced disease. Small GISTs can be endoluminal and polypoid in appearance.
Small and localized GISTs are usually homogeneous, and may be an incidental finding
at CT or endoscopy. Nearly 50% of patients with GISTs present with metastasis.[5] Most metastases of GISTs involve the liver and peritoneum by hematogenous spread
and peritoneal seeding, respectively. Less commonly, metastases are found in the soft
tissue, lungs, and pleura. Calcification within GIST tumors is usually not seen at
presentation but may be seen after treatment.[5]
Fig. 2 Gastrointestinal stromal tumors. (A) Typical appearances of a gastric GIST arising from the lesser curvature with eccentric
location, central necrosis, and peripheral enhancement (arrow). (B) Small uniformly enhancing, polypoid GIST in the duodenum (arrow). (C) Large duodenal GIST showing submucosal location with central necrosis and peripheral
calcification (arrow). (D) Coronal computed tomography image of a large duodenal GIST (short arrow) with a
hypodense liver metastases (long arrow). GIST, gastrointestinal stromal tumor.
Differential diagnosis of GISTs includes schwannomas, true leiomyomas, and solitary
(type 1) carcinoid tumors, particularly for smaller lesions. Occasionally, gastric
adenocarcinoma or lymphoma may demonstrate intramural growth and mimic a GIST. However,
advanced gastric carcinomas and lymphomas are usually associated with bulky perigastric
or celiac lymphadenopathy, which is rare for GISTs.[1] GISTs are known to be associated with neurofibromatosis.[12]
Leiomyoma and Leiomyosarcoma
Leiomyoma and Leiomyosarcoma
Well-documented true gastric leiomyomas and leiomyosarcomas are very infrequent. Older
literature referred to GISTs as leiomyomas; however, true leiomyomas as well as leiomyosarcomas
are negative for c-KIT and strongly and diffusely positive for desmin and smooth muscle
actin.[13] Leiomyosarcoma lesions are usually large, aggressive tumors with heterogeneous enhancement
and areas of necrosis. Their appearance is nonspecific, and histologic confirmation
is required for diagnosis. It is extremely important to accurately differentiate leiomyomas
and leiomyosarcomas from GISTs because GISTs respond favorably to imatinib, whereas
leiomyosarcomas have a less predictable response to conventional chemotherapy. Leiomyomas
are benign while GISTs are associated with risk of progression and metastasis.
In the stomach, small bowel, and colon, GISTs far outnumber leiomyomas. The esophagus
is the only site in the GI tract where leiomyomas predominate. Leiomyomas are almost
always seen in the gastric cardia as homogeneous, low-attenuation masses with an endoluminal
growth pattern, often ranging from 1.3 to 4.7 cm in diameter.[14] Tumors larger than 2 cm can have central ulceration ([Figs. 3]
[4]).
Fig. 3 Leiomyoma seen as a flat, uniformly enhancing lesion with endoluminal projection
in the stomach (arrow).
Fig. 4 Leiomyosarcoma. (A) Axial CT image shows a hypodense, poorly enhancing lesion involving the third part
of duodenum with adjacent infiltration of retroperitoneum (arrow). (B) Coronal CT image shows the hazy infiltration of retroperitoneal fat (arrow). CT,
computed tomography.
Lipomas
Gastric lipomas are composed of mature fat cells surrounded by a fibrous capsule.[15] Patients may present with pain, upper GI bleeding, dyspepsia, and/or gastric outlet
obstruction, although they are typically asymptomatic when small.
On radiographs, a lipoma can occasionally appear as a radiolucent shadow. During fluoroscopy,
a lipoma appears as a smooth well-marginated mass, sometimes with central ulceration.
Three-quarters of lipomas are solitary lesions, with the most common location being
the gastric antrum. The majority (95%) of lipomas are endoluminal, arising in the
submucosa. On CT images, attenuation values of–70 to–120 HU are diagnostic of a lipoma
([Fig. 5]).
Fig. 5 Lipoma. (A) Shows typical appearance of a fat-attenuation, submucosal lesion in the gastric
antrum causing narrowing of the lumen (arrow). (B) Lipoma in the first part of duodenum seen as a fat-attenuation, submucosal lesion.
Peripheral Nerve Sheath Tumors (Neurogenic Tumors)
Peripheral Nerve Sheath Tumors (Neurogenic Tumors)
Gastrointestinal schwannomas are rare neoplasms. Gastrointestinal schwannomas are
distinctly different neoplasms from conventional soft-tissue and central nervous system
schwannomas, some of which may be associated with neurofibromatosis 2.[16] Gastrointestinal schwannomas occur most commonly in the stomach (60–70% of cases),
followed by the colon and rectum[22]. Esophageal and small-intestinal schwannomas have been rarely reported. At clinical
examination, patients may be asymptomatic or present with abdominal pain or GI bleeding
(if the tumor is ulcerated). Larger lesions can manifest with obstructive symptoms.
There is a female predominance among patients with schwannomas, with a median age
of 60 years. Schwannomas arise most often in the gastric body, demonstrating an exophytic
or intramural pattern of growth.
The tumor has low attenuation on CT images because of its dense spindle cell composition.
Contrast-enhanced CT may show no or minimal enhancement ([Fig. 6]). Although cystic degeneration is a common feature of schwannomas found in other
parts of the body, this characteristic is uncommon for gastric schwannomas.[17]
Fig. 6 Schwannoma. (A) A uniformly low attenuation mass is seen at junction of second and third part of
duodenum (arrow). (B) Magnetic resonance imaging shows high signal changes within the mass (arrow).
Neurofibromas are rare tumors that arise from the sympathetic nerves of the Auerbach
myenteric plexus or, less frequently, the Meissner submucosal plexus. Patients with
neurofibromatosis can have multiple neurofibromas and also have increased risk of
malignant degeneration.
Glomus Tumor
Glomus tumors arise from modified smooth muscle cells of the glomus bodies, which
are neuromyoarterial receptors commonly seen in the dermis or subcutis of the extremities
that regulate body temperature.[18] Nearly all GI glomus tumors arise in the muscularis propria of the stomach, and
they account for 2% of all benign gastric tumors. Rare malignant tumors have been
reported for lesions larger than 5 cm.[18]
Glomus tumors most commonly manifest as a solitary hypervascular lesion in the gastric
antrum and range from 1 to 4 cm in diameter.[18] At fluoroscopy, they appear as smooth intramural masses indistinguishable from other
mesenchymal tumors. Because they are soft tumors, glomus tumors can change in shape
and size during fluoroscopy, similar to lipomas. They are easily differentiated from
lipomas on CT images because of their dense arterial phase enhancement, which persists
in the delayed phase ([Fig. 7]). A peripheral nodular pattern of enhancement with delayed filling-in, reminiscent
of a hemangioma, has been reported as a specific feature of gastric glomus tumors.
Fig. 7 Glomus tumor. (A) Intense enhancement is seen in a nodular lesion within the body of stomach (arrow).
(B) The enhancement persists in the delayed venous phase (arrow) which is typical of glomus tumors.
Kaposi Sarcoma
Kaposi sarcoma may occur in the stomach as a mucosal lesion or, less commonly, as
a mural mass, usually in HIV positive patients.[19]
AIDS-related Kaposi sarcoma can affect any level of the GI tract from the oropharynx
to the rectum, including the gallbladder. The duodenum is the most frequently affected
site. The red-purple endoscopic appearance of lesions is helpful in developing the
differential diagnosis, which may include lymphoma, opportunistic infections, hematogenous
metastasis, polyps, and Crohn disease. Early disease is frequently asymptomatic, but
complications (i.e., bleeding, intestinal and biliary obstruction, intussusception,
perforations, diarrhea, and protein-losing enteropathy) may occur as the lesions enlarge.
Double-contrast barium studies may not help detect early flat lesions. Larger lesions
are detected as masses with or without central ulceration (“bull’s eye” or “target”
lesions).[19]
[20] Polypoid submucosal masses 0.5 to 3 cm in diameter, and irregular fold thickening
may be detected at cross-sectional imaging ([Fig. 8]). After the intravenous injection of contrast material, hyperattenuating lymphadenopathies
of the porta hepatis or peripancreatic, retroperitoneal, mesenteric, inguinal, or
pelvic hyperattenuating lymphadenopathies may be seen in approximately 80% of cases
of disseminated KS.19 Bleeding may be a life-threatening complication, often requiring
angiographic diagnosis and treatment.
Fig. 8 Kaposi’s sarcoma. (A) Axial computed tomography image shows polypoid thickening of the duodenum (arrow).
(B) Coronal magnetic resonance imaging HASTE image polypoid changes in the duodenum
with some areas showing the bull’s eye pattern of ulceration. HASTE, Half Fourier
single-shot turbo spin-echo.
Neuroendocrine Tumor
Carcinoid tumors are well-differentiated NETs that originate from the diffuse endocrine
system. In the GI tract, the small bowel is the most common location, followed by
the rectum, appendix, and stomach.[21] Gastric carcinoid tumors are rare, accounting for 1.8% of all gastric malignancies.[22] Carcinoid tumors usually originate from enterochromaffin-like cells (Kulchitsky
cells) in the gastric mucosa and are therefore epithelial in origin.
Of the three types of gastric carcinoids, types 1 and 2 are associated with hypergastrinemia,
which causes proliferation of enterochromaffin like cells and thus promotes the development
of often multiple carcinoid tumors.[23] The majority (75–80%) of gastric carcinoids are type 1, in which patients have atrophic
metaplastic autoimmune gastritis with or without pernicious anemia. Nodal and hepatic
metastases are rare in type 1 carcinoid tumors. Type 2 tumors account for 5 to 10%
of gastric carcinoids and are caused by hypergastrinemia from a gastrin-producing
tumor in association with multiple endocrine neoplasia (MEN) type 1. Approximately
30% of patients with MEN 1 have gastric carcinoid tumors. Type 3 gastric carcinoids
(accounting for roughly 13% of all gastric carcinoids) are sporadic tumors that are
not associated with hypergastrinemia.
At radiologic examination, type 1 gastric carcinoid tumors often appear as multiple
polyps of less than 2 cm in diameter in the gastric fundus, although they can be solitary
([Fig. 9]). Type 2 carcinoids can appear remarkable because of the presence of multiple masses
in the setting of diffuse gastric wall thickening. Unlike type 1 and 2 gastric carcinoids,
type 3 tumors are usually solitary submucosal tumors that may show ulceration and
that are more likely to be recurrent and invasive with distant metastases. The likelihood
of metastasis and perigastric lymphadenopathy depends on tumor size. Prognosis is
poor, with 20% of patients surviving 5 years.
Fig. 9 Neuroendocrine tumors. (A) Computed tomography image shows an arterially enhancing, polypoid lesion in the
body of the stomach (arrow). (B) Magnetic resonance imaging image shows a NET in the stomach (arrow) with multiple cystic liver metastases, some of which show haemorrhagic elements
(short arrow). (C) Octreotide scan in a patient with duodenal NET shows uptake in the tumor (arrow),
lymph nodes (long arrow) and uptake in the liver metastases. NET, neuroendocrine tumor.
Hamartomas
Peutz–Jeghers syndrome is a rare autosomal dominant inherited condition and characterized
by multiple hamartomatous small bowel polyps, which are composed of smooth muscle
and covered by normal mucosa. Peutz–Jeghers polyps are most often found in the jejunum
followed by the ileum and duodenum. The condition is also characterized by mucocutaneous
perioral and genital melanin pigmentation, and increased risk of intestinal adenocarcinoma
and non-GI tumors.
Patients often present with multiple episodes of colicky abdominal pain due to intermittent
intussusception and bleeding. At CT or MRI, hamartomas are seen as smooth, uniformly
enhancing intraluminal masses the bowel ([Fig. 10]).
Fig. 10 A small lobulated hamartoma in the duodenum (arrow) presenting with intussusception.
Lymphoma
Primary gastric lymphoma represents 1 to 5% of gastric malignancies.[24] Gastric lymphoma and is the most common type of extranodal lymphoma and accounts
for 50 to 70% of all primary GI tract lymphomas.[24] Chronic Helicobacter pylori infection is associated with the development of low-grade MALT lymphoma, having been
reported to account for 50 to 72% of all primary gastric lymphomas.[25]
[26] Primary gastric lymphoma often originates as a low-grade MALT lymphoma and transforms
into intermediate or high-grade large cell lymphoma. Low-grade tumors are associated
with a 5-year survival rate of 75 to 91%, compared with a 5-year survival rate of
less than 50% for patients with high-grade MALT lymphomas.
On barium studies lymphomas may appear as multiple polypoid tumors, especially with
central ulceration, giant cavitating lesions, or extensive infiltrative gastric fold
thickening.[24] The stomach remains distensible even in cases with extensive lymphoma involvement,
a crucial differential between lymphoma and linitis plastica. On cross-sectional imaging,
marked gastric wall thickening is present. There may be preservation of perigastric
fat planes and gastric outlet obstruction is rare[27] ([Figs. 11], [12]).
Fig. 11 Lymphoma. (A) Barium meal examination shows thickening of rugal folds (arrow). (B) Large cavitating or aneurysmal ulcer seen in the stomach in lymphoma involvement
(arrow).
Fig. 12 Lymphoma. (A) Coronal CT image shows thickening of rugal folds (arrow). (B) Axial CT image shows marked thickening of the stomach due to lymphoma with aneurysmal
cavitation and dilatation (arrow with multiple lymph nodes around the stomach. CT,
computed tomography.
Bulky lymph nodes are more common with lymphoma than adenocarcinoma particularly if
they extend below the renal hilum. Large cavitating ulcers may also be seen.
