(1)
Department of Pathology, University of Manitoba Max Rady College of Medicine, Winnipeg, MB, Canada
Keywords
Gastrointestinal stromal tumor (GIST)13.1 Introduction
The gastrointestinal tract (GI) can be affected by many of the same soft tissue neoplasms that involve other parts of the body, such as leiomyosarcoma, leiomyoma, schwannoma, and perineurioma. A few soft tissue neoplasms, however, are unique to the gastrointestinal tract. Of these, gastrointestinal stromal tumor is one of the most common. This tumor emanates from the interstitial cells of Cajal that normally coordinate peristalsis for digestion.
13.2 Gastrointestinal Stromal Tumor
On average, gastrointestinal stromal tumors (GISTs) arise in the sixth decade of life, but can be found in patients in all ages, including children. The annual incidence of these tumors is 1.1 per 100,000 people [1]. They can occur anywhere along the enteric tract, but most frequently arise within the wall of the stomach and small bowel [2]. Presenting symptoms include GI bleeding, anemia, or bowel obstruction [3].
These tumors are usually sporadic, but can arise in association with various syndromes, which should be suspected if multiple lesions are identified or if the affected patient is particularly young. Associated syndromes include Carney triad (paraganglioma, pulmonary chondroma, gastrointestinal stromal tumor), Carney-Stratakis syndrome (paraganglioma and gastrointestinal stromal tumor), familial gastrointestinal stromal tumors , and neurofibromatosis [4–6].
Pathology
On gross examination, GISTs are usually fibrous masses in the wall or serosa of the bowel that measure several centimeters in size (Fig. 13.1). Microscopically, they typically show bundles of spindle cells with varying cellularity (Fig. 13.2). Nuclear palisading or perinuclear vacuolization can be identified (Figs. 13.3 and 13.4). The tumor cells can also be epithelioid in appearance (Figs. 13.5 and 13.6).
Fig. 13.1
Gastrointestinal stromal tumor arising in the wall of the stomach. The overlying gastric epithelium is uninvolved
Fig. 13.2
Gastrointestinal stromal tumor with bundles of relatively bland spindle cells
Fig. 13.3
The spindle cells align to form a palisading-type pattern
Fig. 13.4
The spindle cells have clear vacuoles adjacent to the elongated nuclei
Fig. 13.5
This epithelioid appearing gastrointestinal stromal tumor exhibits tumor cells arranged in a vaguely nested architecture
Fig. 13.6
The cells are more rounded and could be mistaken for epithelioid malignancies like carcinoma
Ancillary Studies
Gastrointestinal stromal tumors are positive for cKIT (CD117) or DOG1 immunohistochemical stains [7].
Approximately 80% of GISTs will harbor a mutation in the KIT gene and 7% will harbor a mutation in the PDGFRA gene [8].
GISTs that show no mutation in KIT or PDGFRA have been termed “wild-type” GISTs. These GISTs are still positive for cKIT and/or DOG1 immunohistochemical stains.
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