Gastrointestinal stromal tumour

The gastrointestinal stromal tumour, abbreviated GIST, is uncommon tumour of the GI tract.

General

Epidemiology

Arise from Interstitial cells of Cajal.^[1]
Classically splits the layers of the muscularis propria - as this is where the interstitial cells of Cajal are located.^[2]

Factors predictive of malignant behaviour

Features suggesting a bad prognosis:^[1]

Large size.
- Often benign if small size.
High mitotic rate (for area 5mm^2).
Site - small intestine GISTs worse than stomach GISTs.

Small intestine bad prognosis:^[1]

>5 mitoses/5 mm^2 or size >10 cm.

Stomach bad prognosis:^[1]

>5 mitoses/5 mm^2 and size >5 cm.

Location

Most common locations in order:^[1]

60% in stomach.
35% in small intestine.
5% elsewhere.

Small intestinal GISTs have a worse prognosis than gastric ones.^[1]

Definition

Mutation in the Kit gene or PDGFRA (Platelet-derived growth factor receptor, alpha polypeptide) gene.^[1]

Microscopic

Features:

Classically, spindle cell morphology; however, may be epithelioid (round).
+/-Cytoplasmic inclusions.^[3]

IHC

CD34 +ve in 70%.^[1]
CD117 +ve in 95%.^[1]
- Mast cells are the internal positive control.

Desmin +ve in 5%.^[1]

ICH Work-up panel

S-100 (neural tumours, rarely +ve in GISTs^[1]).
CD34, CD117 (GIST).
Desmin (muscle tumours).

DDx

Leiomyosarcoma.
Leiomyoma.
Neural tumours.
- Neurofibroma.
- Schwannoma (GFAP +ve).
  - GFAP uniformly neg. in GISTs.^[1]

Special tests

Sequence Kit gene, PDGFRA gene.
- Kit gene sequencing is being done more frequently as of late-- if a mutation is found it suggest the drug imatinib will be effective.

Treatment

Imatinib (Gleevec) - drug was developed for chronic myelogenous leukemia.
- There are other similar drugs, e.g. nilotinib and dasatinib.

References

↑ ^1.00 ^1.01 ^1.02 ^1.03 ^1.04 ^1.05 ^1.06 ^1.07 ^1.08 ^1.09 ^1.10 ^1.11 Miettinen M, Lasota J (October 2006). "Gastrointestinal stromal tumors: review on morphology, molecular pathology, prognosis, and differential diagnosis". Arch. Pathol. Lab. Med. 130 (10): 1466–78. PMID 17090188. http://journals.allenpress.com/jrnlserv/?request=get-abstract&issn=0003-9985&volume=130&page=1466.
↑ Agaimy A, Wünsch PH (August 2006). "Gastrointestinal stromal tumours: a regular origin in the muscularis propria, but an extremely diverse gross presentation. A review of 200 cases to critically re-evaluate the concept of so-called extra-gastrointestinal stromal tumours". Langenbecks Arch Surg 391 (4): 322–9. doi:10.1007/s00423-005-0005-5. PMID 16402273.
↑ Pasquinelli G, Severi B, Martinelli GN, Santini D, Gelli MC, Tison V (April 1995). "Gastro-intestinal stromal tumors: an ultrastructural reinterpretation of the clear cell component". J. Submicrosc. Cytol. Pathol. 27 (2): 251–7. PMID 7757951.

[pmid17090188-1] 1.00 ^1.01 ^1.02 ^1.03 ^1.04 ^1.05 ^1.06 ^1.07 ^1.08 ^1.09 ^1.10 ^1.11 Miettinen M, Lasota J (October 2006). "Gastrointestinal stromal tumors: review on morphology, molecular pathology, prognosis, and differential diagnosis". Arch. Pathol. Lab. Med. 130 (10): 1466–78. PMID 17090188. http://journals.allenpress.com/jrnlserv/?request=get-abstract&issn=0003-9985&volume=130&page=1466.

[pmid16402273-2] Agaimy A, Wünsch PH (August 2006). "Gastrointestinal stromal tumours: a regular origin in the muscularis propria, but an extremely diverse gross presentation. A review of 200 cases to critically re-evaluate the concept of so-called extra-gastrointestinal stromal tumours". Langenbecks Arch Surg 391 (4): 322–9. doi:10.1007/s00423-005-0005-5. PMID 16402273.

[pmid7757951-3] Pasquinelli G, Severi B, Martinelli GN, Santini D, Gelli MC, Tison V (April 1995). "Gastro-intestinal stromal tumors: an ultrastructural reinterpretation of the clear cell component". J. Submicrosc. Cytol. Pathol. 27 (2): 251–7. PMID 7757951.

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