| Gastrointestinal stroma tumors (GIST) - in general |
|
GIST are rare mesenchymal tumors of the gastrointestinal
tract (nerve tissue and smooth muscle). They
originate propably from mesenchymal stem cells with a
potential to differentiate. In the classification
of GI-tract tumors they are a relatively new entity.Histology and
Immunhistochemistry discriminate
gastrointestinal stroma tumors from leiomyomas and neurinomas.
The most important location is the stomach. Usually
classic signs of malignancy (cellular invasion, metastasis)
are missing, but a set of histological criteria decides
whether the tumor should be classified as malignant or
benign (mitotic activity, cellular pleomorphism,
developmental stage of the cell and quantity of cytoplasma).
Tumors with a high mitotic activity and a size above 5 cm
are considered to be malignant.
Recent pharmacological advances (Thyrosine kinase inhibitors) have determined c-kit
(i.e. CD117) the most
important marker. C-kit positive tumors respond extremely well to chemotherapy. |
| Gastrointestinal Stroma Tumor (GIST) with arterial hemorrhage |
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| Arterial hemorrhage (Forrest Ia) from
an ulcer on top of a submucous
tumor of the gastric body.
|
The
hemorrhage is successfully treated by injection of 3 ml of
a fibrin-
adhesive. A fibrin string swings from the tumor into the
gastric cavity.
|
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The
tumor measures 4 cm in diameter. The mucosa as such shows
no
pathological changes underlining the submucous location of
the tumor
by means of endoscopy.
|
Surgery
shows the tumor at the dorsal
wall of the gastric body with the ventral
wall opened up by incision. Two superficial ulcers are seen. The lower one is
supposed to be the site of the former
hemorrhage.
Histology reveals a gastrointestinal stroma
tumor (GIST, subtype of a leiomyoma)
with a low mitotic activity.
- eröffnete Magenvorderwand = ventral gastric wall opened up by incision
- Magenhinterwand = dorsal gastric wall
- Ulkus alt/frisch = Ulcer old/ recent
- Längsgastrostomie Korpusmitte = vertical median gastrostomy of the body
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GIST, borderline malignant
potential
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Tumor of the gastric body
more than 5 cm in size. The mucosa
presents normal except a little erythematous. The yellow
colour
shining through the mucosa raises the suspicion of a
lipoma.
A button- whole biopsy fails to establish the diagnosis.
Histologic work- up of the surgical resection specimen
demonstrates a GIST with borderline malignant potential.
(tumor size, vimentin-, MIB1- and desmin positivity).
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| GIST with ulcerations |
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Ulcerations and hemorrhages (see above) do frequently occurr, owing
to the extensive vascularisation of these tumors. |
Artifact
GI-stroma tumor