Cancer: Other GI Tumors Flashcards
Where are leiomyomas typically found in the esophagus?
The distal 1/3.
What is the most common mesenchymal tumor of the esophagus?
Leiomyoma.
How do leiomyomas typically present?
Dysphagia.
Where in GI tract are you unlikely to find leiomyomas?
The stomach and small bowel. They are usually in the esophagus and colon.
What markers are expressed by leiomyomas?
Smooth muscle actin and desmin.
What is the most common mesenchymal tumor of the GI tract?
A gastrointestinal stromal tumor (GIST).
What markers are typically expressed by GISTs?
c-Kit, a tyrosine kinase.
What is the cell of origin for GISTs?
The interstitial cells of Cajal, which are pacemakers for GI motility.
In which layer of the GI tract can the interstitial cells of Cajal typically be found?
In the muscularis propia, near the myenteric plexuses. (They can similarly be found in the muscularis mucosa near submucosal plexuses.)
Why is it thought the GISTs derive from interstitial cells of Cajal?
They both express c-Kit.
What characteristics do GISTs that are c-Kit negative usually have?
(1) epithelioid morphology
(2) PDGFRA mutations
How are GISTs treated?
(1) surgical resection
(2) imatinib, a tyrosine kinase inhibitor (especially effective for c-Kit positives)
(3) sunitinib malate, for the imatinib-resistant
Where in the GI tract are GISTs most common?
The stomach, followed by the small bowel.
What is an important initial indicator of malignancy for GISTs?
Location. 20% of GISTs in the stomach are malignant, compared to half in the small bowel and a majority in the colon and esophagus (though they are rare in these latter locations).
Size and mitotic count are also important.
What genetic disorders are associated with GISTs?
(1) neurofibromatosis type 1
(2) Carney’s triad
What is Carney’s triad?
A generic disorder in young females characterized by:
(1) GISTs
(2) pulmonary chondromas
(3) paragangliomas
What are the 3 general categories of neuroendocrine tumors?
(1) well-differentiated NET
(2) poorly-differentiated neuroendocrine carcinoma, small cell type
(3) poorly-differentiated neuroendocrine carcinoma, large cell type
Where in the wall of the GI tract can neuroendocrine cells typically be found?
They are concentrated at the base of crypts and glands, thus NETs typically develop at the junction of the mucosa and submucosa.
How do NETs appear, grossly?
Yellow-tinged sessile nodules, usually with an intact or slightly eroded surface.
What is a characteristic cytological feature of NETs?
Salt and pepper chromatin.
What are markers of NETs on immunohistochemistry?
(1) synaptophysin
(2) chromogranin
(3) CD56
Which GI tract NETs are more aggressive: functional or non-functional?
Functional.
What causes carcinoid syndrome?
A serotonin-secreting NET.
What is the clinical presentation of carcinoid syndrome?
(1) flushing
(2) diarrhea and abdominal cramps
(3) right-sided heart disease (fibrosis of tricuspid valve)
