Download n Gastric cancer three most common primary malignant gastric

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Gastric cancer
three most common primary malignant gastric neoplasms are adenocarcinoma (95%), lymphoma (4%), and
malignant GIST (1%) (Table 26-14). Other rare primary malignancies include carcinoid, angiosarcoma,
carcinosarcoma, and squamous cell carcinoma. Occasionally the stomach is the site of hematogenous
metastasis from other sites (e.g., melanoma or breast). More commonly, malignant tumors from adjacent
organs invade the stomach by direct extension (e.g., colon or pancreas) or by peritoneal seeding (e.g., ovary).
Aetiology
Gastric cancer is a multifactorial disease. As Helicobacter is associated with gastritis,
gastric atrophy and intestinal metaplasia, the association with malignancy is perhaps not
surprising.
Patients with pernicious anaemia and gastric atrophy are at increased risk, as are those
with gastric polyps. Patients who have had peptic ulcer surgery,particularly those who
have had drainage procedures such as Billroth II or Pَlya gastrectomy,
gastroenterostomy or pyloroplasty, are at approximately four times the average risk.
Presumably, duodenogastric reflux and reflux gastritis are related to the increased risk of
malignancy in these patients. Intestinal metaplasia is a risk factor. Carcinoma is
associated with cigarette smoking and dust ingestion from a variety of industrial
processes.
Diet appears to be important, The ingestion of substances
such as spirits may induce gastritis and, in the long term, cancer. Excessive salt intake,
deficiency of antioxidants and exposure to N-nitroso compounds are also implicated.
The aetiology of proximal gastric cancer associated with obesity and higher socioeconomic status.Genetic factors are also important but imperfectly elucidated .
Clinical features
Curable gastric cancer has no specific features to distinguish it symptomatically from
benign dyspepsia. The key to improving the outcome of gastric cancer is early diagnosis
and, a high index of suspicion is necessary, as endoscoping only patients with symptoms
of advanced cancer is unlikely to be beneficial because such patients are not surgically
curable. It is important to note that gastric anti-secretory agents will improve the
symptoms of gastric cancer so the disease should be excluded preferably before therapy
is started.
In advanced cancer, early satiety, bloating, distension and vomiting may occur. The
tumour frequently bleeds, resulting in iron-deficiency anaemia. Obstruction leads to
dysphagia, epigastric fullness or vomiting. With pyloric involvement the presentation
may be of gastric outlet obstruction, although the alkalosis is usually less pronounced or
absent compared with cases of duodenal ulceration leading to obstruction. Metastatic
lymph nodes may be palpable, most notably in the left supraclavicular fossa (Virchow’s
node, Troisier’s sign Non-metastatic effects of malignancy are seen, particularly
thrombophlebitis (Trousseau’s sign) and deep venous thrombosis. These features result
from the effects of the tumour on thrombotic and haemostatic mechanisms.
Gastric cancer Site
The lower oesophagus is also a very common site of adenocarcinoma, 60% of all of
the malignancies occurring in the oesophagus and stomach occur in proximity to the
oesophagogastric junction.
Pathology
The most useful classification of gastric cancer is the Lauren classification.
: intestinal gastric cancer and diffuse gastric cancer. In intestinal gastric cancer, the
tumour resembles carcinomas found elsewhere in the tubular gastrointestinal tract and
forms polypoid tumours or ulcers. It probably arises in areas of intestinal metaplasia. In
contrast, diffuse gastric cancer infiltrates deeply into the stomach without forming
obvious mass lesions but spreading widely in the gastric wall. this has a much worse
prognosis.
Gastric cancer can be divided into early gastric cancer and advanced gastric cancer.
Early gastric cancer can be defined as cancer limited to the mucosa and submucosa with
or without lymph node involvement (T1, any N); In the Japanese classification, early
gastric cancer can be protruding, superficial or excavated. Early gastric cancer is
eminently curable, and even early gastric cancers associated with lymph node
involvement have 5-year survival rates in the region of 90%.
Advanced gastric cancer involves the muscularis. Its macroscopic appearances have
been classified by Bormann into four types). Types III and IV are commonly incurable.
Staging
The International Union Against Cancer (UICC) staging systemis shown in Table 60.5.
Spread of carcinoma of the stomach
this distant spread is unusual before the disease spreads locally, and distant metastases
are uncommon in the absence of lymph node metastases. The intestinal and diffuse types
of gastric cancer spread differently. The diffuse type spreads via the submucosal and
subserosal lymphatic plexus and it penetrates the gastric wall at an early stage.
Direct spread
The tumour penetrates the muscularis, serosa and ultimately adjacent organs such as the
pancreas, colon and liver.
Lymphatic spread
This is by both permeation and emboli to the affected tiers of nodes. This may be
extensive, with the tumour even appearing in the supraclavicular nodes (Troisier’s sign).
Unlike malignancies such as breast cancer, nodal involvement does not imply systemic
dissemination
Table 60.5 International Union Against Cancer (UICC) staging of gastric cancer
T1 Tumour involves lamina propria T2 Tumour invades muscularis or subserosa
T3 Tumour involves serosa
T4 Tumour invades adjacent organs
N0 No lymph nodes N1 Metastasis in 1–6 regional nodes N2 Metastasis in 7–15
regional nodes
N3 Metastasis in more than 15 regional nodes
M0 No distant metastasis
M1 Distant metastasis (this includes peritoneum and
distant lymph nodes)
The prognosis of operable cases of carcinoma of the stomach depends on whether or not
there is histological evidence of regional lymph node involvement. Retrograde
(downwards) spread may occur if the upper lymphatics are blocked.
Operability
It is important that patients with incurable disease are not subjected to radical surgery
that cannot help them, hence the value of CT/PET). Unequivocal evidence of
incurability is haematogenous metastases, involvement of the distant peritoneum, N4
nodal disease and disease beyond the N4 nodes, and fixation to structures that cannot be
removed. It is important to note that involvement of another organ per se does not imply
incurability, provided that it can be removed. Most operable patients should have
neoadjuvant chemotherapy as described below, as this improves survival.
Radiotherapy
The routine use of radiotherapy is controversial There are a number of radiosensitive tissues in the region of the gastric bed,
which limits the dose that can be given. Radiotherapy has a role in the palliative treatment of painful bony metastases
.Chemotherapy
Gastric cancer may respond well to combination cytotoxic chemotherapy and
neoadjuvant chemotherapy improves the
outcome following surgery. Therefore, most patients should have chemotherapy before
surgery.
GASTRIC LYMPHOMA
. It
is first important to distinguish primary gastric lymphoma from involvement of the
stomach in a generalised lymphomatous process. This latter situation is more common
than the former. Primary gastric lymphoma accounts for approximately 5% of all gastric
neoplasms. Gastric lymphoma is most prevalent in the sixth decade of life. The
presentation is no different from gastric cancer, the common symptoms being pain,
weight loss and bleeding. Acute presentations of gastric lymphoma such as
haematemesis, perforation or obstruction are not common. Primary gastric lymphomas
are B cell-derived, the tumour arising from the mucosa-associated lymphoid tissue
(MALT). Diagnosis is made as a result of the endoscopic biopsy and seldom
on the basis of the endoscopic features alone, which are not specific.
Following diagnosis, adequate staging is necessary, primarily to establish whether the
lesion is a primary gastric lymphoma or part
of a more generalised process. CT scans of the chest and abdomen and bone marrow
aspirate are required, as well as a full blood count. Although the treatment of primary
gastric lymphoma is somewhat controversial, it seems most appropriate to use surgery
alone for the localised disease process. No benefit has been shown from adjuvant
chemotherapy, although some oncologists contend that primary gastric lymphoma can
be treated by chemotherapy alone. Chemotherapy alone is appropriate for patients with
systemic disease
GASTROINTESTINAL STROMAL TUMOURS
Gastrointestinal stromal tumours (GISTs) commonly occur in the stomach and
duodenum. Previously named leiomyoma and leiomyosarcoma, the term GIST is now
used, recognising their particular distinct phenotype. The tumours are universally
associated with a mutation in the tyrosine kinase c-kit oncogene. These tumours are
sensitive to the tyrosine kinase antagonist imatinib, and an 80% objective response rate
can be observed. and liver metastases are most common; spread to lymph nodes is
extremely rare.; small stromal tumours of the stomach are probably quite common but
remain unnoticed. Clinically obvious tumours are considerably less common than gastric
cancer. The only way that many stromal tumours are recognised is either that the
mucosa overlying the tumour ulcerates , leading to bleeding, or that they are noticed
incidentally at endoscopy.. Because the mucosa overlying the tumour is normal,
endoscopic biopsy can be uninformative unless the tumour has ulcerated. Larger
tumours present with non-specific gastric symptoms.
.
the best guide of malignancy is to consider the size of the tumour. If easily resectable,
surgery is the primary mode of treatment. Smaller tumours can be treated by wedge
excision although the appropriate management of asymptomatic diminutive tumours
found incidentally at endoscopy is unclear. Larger tumours may require a gastrectomy or
duodenectomy 6but lymphadenectomy is not required. Larger tumours that require
multivisceral resection may be better .
Zollinger–Ellison syndrome
the gastrin-producing endocrine tumour is often found in the duodenal loop, although it
also occurs in the pancreas, especially the head. It is a cause of persistent peptic
ulceration. Before the development of potent gastric anti-secretory agents,
.
. The advent of proton pump inhibitors has rendered this extreme endocrine condition
fully controllable, but also less easily recognised. Gastrinomas may be either sporadic or
associated with the autosomal dominantly inherited multiple endocrine neoplasia (MEN)
type I (in which a parathyroid adenoma is almost invariably present). The tumours are
most commonly found in
the ‘gastrinoma triangle’ (Passaro) defined by the junction of the cystic duct and
common bile duct superiorly, the junction of the
second and third parts of the duodenum inferiorly, and the junction of the neck and body
of the pancreas medially (essentially
the superior mesenteric artery).
It is extremely important that the duodenal wall is very carefully inspected
endoscopically and also at operation. Very often all that
can be detected is a small nodule that projects into the medial wall of the duodenum.
Even malignant sporadic gastrinomas may have a very indolent course. The palliative
resection of liver metastases may be
beneficial and, as for other gut endocrine tumours,
In MEN type I, the tumours may be multiple and the condition is incurable. Even in this
situation, as with sporadic
gastrinoma, surgical treatment should be employed to remove any obvious tumours and
associated lymphatic metastases, as the
palliation achieved may be good.
Acute gastric dilatation
This condition usually occurs in association with pyloroduodenal disorders or after
surgery without nasogastric suction. The stomach, which may also be atonic, dilates
enormously. Often the patient is also dehydrated and has electrolyte disturbances.
Failure to treat this condition can result in a sudden massive vomit with aspiration into
the lungs. The treatment is nasogastric suction with a large-bore tube, fluid replacement
and treatment of the underlying condition.
Trichobezoar and phytobezoar
Trichobezoars (hair balls) are unusual and are almost exclusively found in female
psychiatric patients, often young.
They are caused by the pathological ingestion of hair, which remains undigested in the
stomach. The hair ball can lead to ulceration and gastrointestinal bleeding, perforation or
obstruction. The diagnosis is made easily at endoscopy or, indeed, from a plain
radiograph. Treatment consists of removal of the trichobezoar, which may require open
surgical treatment. Phytobezoars are made of vegetable matter and are found principally
in patients who have gastric stasis. Often this follows gastric surgery.