Download Gastric Cancer 16

Gastric Cancer
16
Gastric Cancer
Jiro Hata, Ken Haruma, Noriaki Manabe, Tomoari Kamada,
Hiroaki Kusunoki, Toshiaki Tanaka, and Motonori Sato
transabdominal ultrasound due to its invasiveness. In
this chapter, sonographic imaging of gastric cancer,
mainly transabdominal, is described.
CONTENTS
16.1
Introduction 135
16.2
Sonographic Assessment of
the Gastric Wall 135
16.2.1 Preparation and Equipment 135
16.2.2 Sonographic Image of
the Normal Gastric Wall 135
16.3 Sonographic Features of Gastric Cancer 136
16.3.1 Early Gastric Cancer 136
16.3.2 Advanced Gastric Cancer 138
16.4
Staging of Gastric Cancer
16.5
Conclusion 141
135
140
References 142
16.1
Introduction
Gastric cancer is still of major importance worldwide despite declining incidence. Endoscopy, radiological examination, and computed tomography are
the diagnostic imaging modalities employed for
gastric cancer. For early gastric cancers, in particular, endoscopy is the essential diagnostic method of
choice; however, with the remarkable improvements
in sonographic equipment, transabdominal ultrasonography has recently been reported to be useful in
the assessment of gastric cancer. Endoscopic ultrasound is another imaging modality using ultrasound
which has not necessarily been as widely used as
J. Hata, MD
Department of Clinical Pathology and Laboratory Medicine,
Kawasaki Medical School, 577, Matsushima, Kurashiki-city,
Okayama, 701-0192, Japan
K. Haruma, MD; N. Manabe, MD; T. Kamada, MD;
H. Kusunoki, MD; T. Tanaka, MD; M. Sato, MD
Division of Gastroenterology, Dept. of Internal Medicine,
Kawasaki Medical School, 577, Matsushima, Kurashiki-city,
Okayama, 701-0192, Japan
16.2
Sonographic Assessment of
the Gastric Wall
16.2.1
Preparation and Equipment
For the screening of advanced gastric cancers, special
preparations, such as the ingestion of water, and the
injection of anticholinergic agents, are not necessary
in most cases; however, such preparations are required
to visualize smaller lesions. After an overnight fast,
the ingestion of approximately 200–400 ml of water
makes it easier to detect smaller lesions located in the
posterior wall of the gastric circumflex. The injection
of spasmolytic agents is seldom necessary.
While a 3–4 MHz curved array scanner is used for
routine screening for gastric cancers, detailed examination including the evaluation of wall stratification
should be performed with a high-frequency (5–
9 MHz) linear probe for its superior spatial resolution. Tissue harmonic imaging is also recommended
to reduce noises such as side lobe artifacts (Laing
and Kurtz 1982).
16.2.2
Sonographic Image of the Normal Gastric Wall
The abdominal esophagus is visualized between the
abdominal aorta and the left lobe of the liver by a left
middle subcostal scan. Below the abdominal esophagus lies the gastric fundus. The gastric body is usually
located in the left middle upper abdomen. The gastric
fold is often observed at the greater curvature of
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the gastric body (Fig. 16.1). Gastric antrum is located
in the right middle upper abdomen. The pylorus is
identified as the segmental thickening of the proper
muscle (Fig. 16.2). The thickness of the normal gastric wall is usually <5 mm, and wall thickening of
>6 mm is considered pathological.
The normal gastric wall is demonstrated as a fivelayer structure. The first layer is hyperechoic, and
corresponds to the luminal boundary and part of the
mucosal layer. The second layer is hypoechoic and
includes the remaining part of the mucosa and mucosal muscle layer. The third layer is hyperechoic and
corresponds to the submucosal layer. The fourth layer
is hypoechoic and corresponds to the proper muscle
layer. The fifth layer is hyperechoic and corresponds
to the serosa and the extramural boundary.
Fig. 16.1. Transverse scan of the gastric body. The five-layer
structure of the gastric wall and the gastric fold are demonstrated
16.3
Sonographic Features of Gastric Cancer
16.3.1
Early Gastric Cancer
It is not always easy, and often rather difficult, to detect
early gastric cancer by means of routine ultrasonographic screening, because both the wall thickening
and alteration of wall stratification are too subtle to
be detected with transabdominal ultrasound. In this
respect, ingestion of water is useful to obtain a clear
image of such subtle changes.
Early gastric cancer is usually expressed as focal
wall thickening originating in the second layer. No
changes of the submucosal layer are shown with
intramucosal cancer (Fig. 16.3). When the tumor
invades the submucosal layer, the shape and the
width of that layer changes (Fig. 16.4) and it finally
disappears as the tumor invades the proper muscle;
however, the evaluation of cancer invasion becomes
difficult when it is complicated by an ulcer, because
the fibrosis accompanying ulcer healing is expressed
as a hypoechoic area which resembles cancer. The
diagnostic accuracy of determination of cancer
depth with transabdominal ultrasound is generally thought to be inferior to that with endoscopic
ultrasound, which provides a clear image with fewer
artifacts and high resolution, although there are
several contradictory reports (Ishigami et al. 2004;
Meining et al. 2002). Even with endoscopic ultrasound, however, it is difficult to differentiate fibrotic
tissue from cancer.
Fig. 16.2. Longitudinal scan of the
gastric antrum and the duodenal
bulb. The gastric lumen is filled
with water
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Gastric Cancer
a
b
c
Fig. 16.3. a Sonographic image of an early (intramucosal) gastric cancer. Focal wall thickening, which is limited to the mucosal
layer, is demonstrated. b Endoscopic feature of the same patient as shown in a. A focally elevated lesion with an ulcer at the
center is visualized. c Sonographic image of an early (intramucosal) gastric cancer. Focal wall thickening with an indentation
at the center is demonstrated. No narrowing of submucosal layer is observed
a
b
Fig. 16.4. a Sonographic image of an early (submucosal invasion) gastric cancer. Narrowing of the submucosal layer is demonstrated. b Endoscopic sonography of an early gastric cancer (submucosal invasion). There is narrowing of the submucosal
layer beneath the tumor
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16.3.2
Advanced Gastric Cancer
Advanced gastric cancer is demonstrated as focal
wall thickening without wall stratification (Figs. 16.5,
16.6). The typical sonographic figure is a “pseudokidney sign,” i.e., an echogenic area surrounded by a
hypoechoic rim that resembles the image of kidney.
Exceptionally, in scirrhous cancers, wall stratification
is demonstrated, although it is somewhat blurred
(Figs. 16.7, 16.8). The lesions of advanced gastric
cancer show poor compliance and compressibility,
as well as reduced peristalsis or even loss of it. The
vascularity on color/power Doppler depends on the
nature of cancer and may not necessarily be useful
for differentiation between benign and malignant
conditions.
Differential diagnoses should be decided among
the following: benign gastric ulcer, malignant lymphoma, acute gastric mucosal lesion, and anisakiasis,
and ultrasound is useful for this purpose (Okanobu
et al. 2003). Benign gastric ulcers show focal wall
thickening with a wall defect at the center. Since the
wall thickening around the ulcer is due to submucosal edema, wall stratification is basically preserved.
Malignant lymphoma also shows focal wall thickening without stratification which resembles advanced
gastric cancer, but the thickened wall is characterized by very low echogenicity, often lower than that
of gastric carcinoma. Acute gastric mucosal lesions
and gastric anisakiasis are characterized by diffuse
wall thickening with wall stratification, brought on
mainly by submucosal edema, which occasionally
resembles scirrhous cancer. In scirrhous cancers, the
width of every layer is irregular, and the boundary
of each layer is often blurred. Furthermore, the compressibility/compliance is poor and the peristalsis is
remarkably reduced.
Fig. 16.5. a Advanced gastric cancer. Wall stratification has
been totally destroyed and the extramural margin is irregular.
b Endoscopic image of the same case as shown in Fig. 16.5a.
c Endoscopic ultrasound image of an advanced gastric cancer.
Focal wall thickening without wall stratification is observed
a
b
c
Gastric Cancer
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a
a
b
b
c
Fig. 16.6. a Transverse scan of advanced gastric cancer at the
cardia. Wall thickening without stratification is seen in almost
all circumferences, accompanied by luminal narrowing. b Longitudinal scan of the same lesion as shown in Fig. 16.6a. c Endoscopic view of the same case
c
Fig. 16.7. a Longitudinal scan of pyloric stenosis due to an advanced
gastric cancer. Diffuse wall thickening of the antrum is demonstrated.
b Close-up view of the posterior wall of the antrum with a 7-MHz linear
probe. Wall stratification has not been completely destroyed. c Endoscopy reveals marked luminal narrowing
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a
c
b
d
Fig. 16.8. a Schirrous-type gastric cancer in the gastric body. Note the difference in gastric compliance at the antrum and the lesion. b Close-up view of the lesion with a 7-MHz linear probe. Wall stratification is demonstrated. c Schirrous-type gastric cancer
at the fornix. Diffuse wall thickening at the fornix and ascites (asterisk) are demonstrated. d Endoscopic image of giant rugae
16.4
Staging of Gastric Cancer
For the staging of gastric cancer, cancer depth and
metastases (to remote organs, lymph nodes, the peritoneum) must be assessed. There have been a few
reports on the cancer staging with ultrasound showing high diagnostic ability (Liao et al. 2004; Lim et
al. 1994).
The depth of cancer for an early gastric cancer is
decided by assessment of alteration of wall stratification. The extension of an advanced gastric cancer is
decided by careful evaluation of the tumor margin.
When the outer margin of the tumor is smooth and a
fat pad or boundary echo is observed between every
other contiguous organ and the tumor, the cancer
is considered to be within the serosa. Irregularity
of the outer margin suggests high risk of the tumor
exceeding the serosa. Loss of the boundary echo
accompanied by loss of sliding movement between
other organs are important findings suspicious of
minimal invasion into an adjacent organ. The invasion is obvious when the tumor boundary lies in the
contiguous organ and deforms the contour of the
organ (Fig. 16.9).
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a
a
b
Fig. 16.9. a Gastric cancer invasion into the tail of the pancreas is demonstrated. The hypoechoic tumor has altered the
contour of the pancreas tail. b Gastric cancer invasion into the
transverse colon. This hypoechoic tumor is compressing the
upper circumference of the transverse colon and the boundary
echo between them has disappeared
Typical metastatic liver tumors have a thick
hypoechoic rim with a relatively hyperechoic center,
known as the “bull’s-eye” sign (Fig. 16.10a); however,
this finding cannot be applied to all metastatic liver
tumors. Penetration of the normal vascular structure
through the tumor proven by color/power Doppler,
ring-shaped enhancement in the arterial phase, and
loss of enhancement in the postvascular phase as
determined by contrast ultrasound, are helpful findings for the diagnosis of metastatic liver tumors.
Lymph node metastases are characterized by the
round-shaped swelling of lymph nodes (Fig. 16.10b).
One must be careful in the differentiation from
inflammatory swelling of lymph nodes caused by a
benign gastric ulcer, which is more elliptical in shape
than that of metastatic lymph nodes.
Tumor seeding is demonstrated as a hypoechoic
nodule on the visceral or parietal peritoneum
(Fig. 16.10c). Often ascites with floating echogenic
particles accompanies tumor seedings, indicating
peritonitis carcinomatosa.
b
c
Fig. 16.10. a Metastatic liver tumors are demonstrated.
b Metastatic lymph nodes (ln) around the superior mesenteric
artery (sma) are demonstrated. c A seeding nodule (asterisks)
seen in a patient with advanced gastric cancer
16.5
Conclusion
Although influenced by the patients’ constitution and
the skill of the operator, transabdominal ultrasound
can be a useful diagnostic tool for the evaluation of
gastric cancer.
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J. Hata et al.
References
Ishigami S, Yoshinaka H, Sakamoto F et al (2004) Preoperative
assessment of the depth of early gastric cancer invasion
by transabdominal ultrasound sonography (TUS): a comparison with endoscopic ultrasound sonography (EUS).
Hepatogastroenterology 51:1202–1205
Laing FC, Kurtz AB (1982) The importance of ultrasonic sidelobe artifacts. Radiology; 145:763–8
Liao SR, Dai Y, Huo L et al (2004) Transabdominal ultraso-
nography in preoperative staging of gastric cancer. World
J Gastroenterol 23:3399–3404
Lim JH, Ko YT, Lee DH (1994) Transabdominal US staging of
gastric cancer. Abdom Imaging 19:527–531
Meining A, Dittler HJ, Wolf A et al (2002) You get what you
expect? A critical appraisal of imaging methodology in
endosonographic cancer staging. Gut 50:599–603
Okanobu H, Hata J, Haruma K et al (2003) Giant gastric
folds: differential diagnosis at US. Radiology 228:986–
990