1.Concept of gastrointestinal mesenchymal tumor
In the 1940s, spindle cell tumors occurring in the mesenchymal origin of the gastrointestinal tract were clinically referred to as smooth muscle tumors (leiomyoma) or smooth muscle sarcoma (leiomyosarcoma). 1960 Matin in France first described six cases of smooth muscle tumors occurring in the stomach with epithelial-like morphological features, which were thought to originate from smooth muscle mother cells and were called smooth muscle The origin of these tumors was thought to be from smooth muscle mother cells, and they were called smooth muscle blastoma and malignant smooth muscle blastoma. Yan Zu, Department of Surgical Oncology, Qinghai University Hospital
In fact, in 1983, Mazur and Clark studied smooth muscle tumors of the stomach and found that most tumors lacked ultrastructural and immunophenotypic features of smooth muscle cells or Schwann’s cells, and subsequently adopted the term “stromal tumor” to designate these tumors that are difficult to differentiate in a clear direction, and gastrointestinal stromal tumor (GIST).
GIST is a gastrointestinal mesenchymal tumor of mesenchymal origin that expresses KIT protein (CD117) immunophenotypically, has frequent c-kit mutations genetically, and is characterized histologically by a fasciculated crossover or diffuse arrangement of spindle cells and epithelioid cells.
GIST accounts for 2.2% of gastric malignancies, 13.9% of small bowel malignancies, and 0.1% of colorectal malignancies, for a total of approximately 2% of GI tract tumors. Among the mesenchymal-derived tumors of the gastrointestinal tract, GIST is more common.
2. Clinical characteristics of gastrointestinal mesenchymal tumors
There is little difference in the incidence rate between men and women, and the peak incidence is between 55 and 65 years old. Gastric mesenchymal tumor accounts for 60%-70%, small intestinal mesenchymal tumor accounts for 20%-30%, colorectal mesenchymal tumor accounts for 18.1%, esophageal mesenchymal tumor accounts for 1.4%, in addition, other parts such as abdominal soft tissue (omentum, mesentery) and retroperitoneum can occur, also known as extra-gastrointestinal stromal tumor (EGIST). When the tumor is small, it is asymptomatic, but when the tumor increases, symptoms may appear.
Gross morphology: no envelope, mostly located between the muscle wall, a few located in the plasma membrane layer. Biological behavior: tumor <2cm is benign, tumor >5cm is malignant, in between is junctional tumor.
3.Diagnostic criteria of GIST
In fact, the differential diagnosis is mostly made by immunohistochemistry at present.
The positive rate of KIT (CD117) is 96%.
nestin positive rate 88%
CD34 positive rate 77.2%
Please note that a minority of GISTs do not express CD117. In addition, GISTs have varying degrees of SMA, s-100, destin, MSA and PGP9.5 expression.
4.Treatment
The first choice is surgical resection, which requires a certain safe margin of incision and the tumor should not be broken as much as possible to prevent medical dissemination. Postoperative treatment is supplemented with Glivec (imatinib) orally.
5.Problems
It is very easy to local recurrence after surgery, and a few occur distant metastasis. Glivec may be ineffective in a proportion of patients without c-kit gene activating mutations.
6.My experience
Once detected, surgical resection should be performed as early as possible. Pay attention to the key points of surgical operation: a. Do not break the tumor; b. Do not accumulate the tumor; c. Ensure safe cutting edge. For malignant GIST it is recommended to take oral Gleevec after surgery and do regular follow-up after surgery, preferably once in 3 months after surgery and change to once every 6 months after 1 consecutive year.