GIST accounts for 1-3% of all gastrointestinal tumors. They arise from interstitial cells of cajal
(ICC) that are normally part of autonomic nervous systems of the intestine.
They are distinct from leiomyoma and leiomyosarcoma which are smooth muscle cells tumors. They are non epithelial tumors. 50-70% occurs in the stomach, 10- 20% in the small intestine and 10% in other parts of GIT(colon,rectum, esophagus, mesentery) .
Prognosis
Depends mostly on tumor size, mitotic count and metastasis.
Low grade lesions without metastasis are cured by resection.
High grade lesions with metastasis have 5year survival of less than 30%. Any tumor with size more than 1cm can behave in a malignant fashion.
Almost all GIST express c-kit proto-oncogene and thus these are very responsive tyrosine kinase antagonists like imatinib and almost all smooth muscle tumors express actin and desmin and these markers are very useful in differentiation between GIST and smooth muscle tumor.
The metastasis occurs in liver and peritoneum but spread to the lymph nodes is extremely rare.
They are difficult to diagnose endoscopically
because mucosa over the tumor appears normal until it ulcerates. They may be asymptomatic or they can cause symptoms just like carcinoma of the stomach.
Treatment is surgery Small tumors can be treated by wedge excision and large tumors
may need gastrectomy.
Larger tumors may need preoperative treatment Imatinib to shrink the tumor and to reduce its
vascularity before surgery.
GASTRIC LYMPHOMA:
Gastric lymphoma can be a primary malignancy of the stomach (primary gastric lymphoma) or it
can be a part of generalized lymphoma of the body (secondary gastric lymphoma).
Primary gastric lymphoma:
Primary gastric lymphoma arises on the background of chronic gastritis as the normal stomach is devoid of lymphoid tissue. In the setting of chronic gastritis the stomach acquires mucosal associated lymphoid tissue degeneration. H.pylori is thought to be main (MALT) which can undergo malignant
Causative factors.
Over 95% of primary gastric lymphoma are non Hodgkin B-cell type.
They range from low grade to poorly differentiated high grade lymphoma (difficult to differentiate from adenocarcinoma
Whenever without immunohistochemistry). primary gastric lymphoma is encountered; CT scan of the abdomen, thorax and pelvis should be performed to rule out systemic lymphoma.
Treatment:
low grade gastric lymphoma associated with H.pylori infection often regress (70-95%) with eradication therapy (antibiotics and PPI).
No definite guidelines have been advocated for the treatment of advanced or H. pylori negative MALT-type of gastric lymphoma and for low grade lymphoma that persists after H.pylori eradication.
Although surgery has been used as its initial treatment, recent studies showed that radiotherapy alone can achieve a complete remission with a 5-year disease free period and for stage I disease while systemic chemotherapy for more advanced disease.
Secondary gastric lymphoma:
it is treated according to stage and variety of lymphoma.
Bezoars: A bezoars is a mass found trapped in the gastrointestinal system (usually the stomach
Trichobezoar: it is mass of hair balls, uncommon condition exclusively found in psychiatric females caused by ingestion of hair, which remains undigested in the stomach
Phytobezoar: are made of vegetable matter found principally in patients who have gastric stasis
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