carcinoid tumor

1. Gastric Lymphoma,
Carcinoid Tumor and GIST
Thomas Rosenzweig, MD

2. MALToma
(Extranodal marginal zone B-cell lymphomas)
 Two Causes:
 H. pylori
 NF-κB activation via MLT/BCL-10 pathway in normal MALTomas
(without the below translocations)
 H. pylori treatment is effective
 t(11;18) ↑MALT1
 (q21;q21) ↑BCL-10
 Normally, activation of NF-κB in B and T cells requires
both BCL-10 and MALT1. (Here, only one activates it.)
 H. pylori treatment is ineffective
constitutive activation of NF-κB,
↑ B-cell growth and survival.
*In the stomach these tumors are called lymphomas
of mucosa-associated lymphoid tissue (MALT), or MALTomas.
*MALT is usually caused by chronic gastritis (H. Pylori)

3.  Symptoms = dyspepsia and epigastric pain
 Lymphoepithelial lesions
 gastric MALToma takes the form of a dense lymphocytic
infiltrate in the lamina propria
 MALTomas can develop into diffuse B-cell lymphomas
 No longer responsive to H. pylori eradication
 Happens with additional genetic changes
 (inactivation of p53 and p16)
 express the B-cell markers CD19 and CD20 and CD43
 do not express CD5 or CD10
MALToma
(Extranodal marginal zone B-cell lymphomas)

4. Carcinoid Tumor

5. Carcinoid Tumor
 60 years old
 Location Matters!
 Foregut carcinoid tumors (stomach, duodenum proximal to the ligament of Treitz, and
esophagus)
 rarely metastasize
 Midgut carcinoid tumors (jejunum and ileum)
 aggressive
 Hindgut carcinoids (appendix and colorectum)
 typically discovered incidentally and are benign
 Hormones determine symptoms
 Duodenum Tumors cause Zollinger-Ellison syndrome from gastrin
 Ileal tumors cause carcinoid syndrome
 (cutaneous flushing, sweating, bronchospasm, colicky abdominal pain, diarrhea, and
right-sided cardiac valvular fibrosis.)
 vasoactive substances secreted by the tumor into the systemic circulation (Causes
metastatic disease in the liver)
 When tumors are confined to the intestine, the vasoactive substances released are
metabolized to inactive forms by the liver, a “first-pass” effect
 Exceptions: large tumor or when tumors secrete hormones into a nonportal
venous circulation.

6. Carcinoid Tumor
– yellow or tan in color and
very firm
– pink granular cytoplasm
and a round / oval nucleus.
• minimal pleomorphism
– Stains are + for
synaptophysin and
chromogranin A

7. Features of GI Carcinoid Tumors

8. Mesenchymal Neoplasms
 Leiomyomas
 smooth muscle tumors
 Schwannomas
 nerve sheath tumors
 Glomus tumors
 resemble glomus bodies in the nail beds and other sites
 GI stromal tumor (GIST)
 most common mesenchymal tumor of the abdomen
 Usually in the stomach

9. GI stromal tumor (GIST)
 GI stromal tumor (GIST)
 from interstitial cells of Cajal (pacemaker cells)
 most common mesenchymal tumor of abdomen
 60 years old (usually in the stomach)
 Mutations result in constitutively
active KIT or PDGFRA
 KIT gain-of-function (stain)
 platelet-derived growth factor receptor
α (PDGFRA)
*Likely on test
GIST KIT Stain

10. GI stromal tumor (GIST)
 Spindle cell type
 composed of thin elongated cells
 Epithelioid type
 epithelial-appearing cells
 Gastric GISTs are less aggressive than small
intestine
 Smaller than 5cm = safe
 Larger than 10cm = metastasis
 Treatment: imatinib (for mutations in KIT or
PDGFRA)
 development of imatinib-resistance is
common, due to secondary KIT or
PDGFRA mutations

11. Key Concepts