GASTROINTESTINAL STROMAL TUMOUR OF STOMACH
Dharmesh J Balsarkar*, V M Deshmukh**,Geeta Ghag*, Mohan Joshi***
*Lecturer; **Honorary Professor, ***Professor, Department of General Surgery, LTMMC and LTMGH, Sion, Mumbai 400
GISTs constitute the largest category of primary neoplasms of stomach and bowel. We report a case of intraluminal GIST of stomach.
Gastrointestinal stromal tumours (GISTs) constitute the largest category of primary nonepithelial neoplasms of the stomach and small bowel. They arise from cells located in the walls of the organ and show a remarkable variability in their differentiation pathways. This has resulted in a considerable degree of confusion in their interpretation, which if anything it has exacerbated recently. For many years, they were all regarded as being basically of smooth muscle nature and designated as leiomyomas and leiomyosarcomas when composed of spindle cells and as benign or malignant leiomyoblastomas (or epithelioid leiomyomas and leiomyosarcomas, respectively) when composed of epithelioid cells. The many immunohistochemical and ultrastructural studies that have been carried out by numerous authors in recent times have shown a much more complex picture. We report herewith a case of intraluminal GIST of the stomach.
A 50 year old postmenopausal female patient presented to us with complaints of pain in upper abdomen since one year. No other positive history was elicited. On examination, her vital parametes were normal. No significant abdominal findings were noted. Patient underwent an upper GI endoscopy, which showed a large pedunculated growth measuring approximately 7 x 3 x 2 cm. on the posterior wall of the stomach. Rest of the endoscopy was normal (Fig. 1). Her haematological investigations and USG abdomen were normal.
In view of the above findings, a decision to undertake operative excision of the growth was made. At laparotomy, the growth was palpable in the body of the stomach in the posterior wall towards the greater curvature, which was approached via an anterior gastrostomy. The growth was excised after incising the posterior wall mucosa around the base of the growth and checking for the intergrity of the posterior wall. Posterior wall mucosa around the base of the growth and checking for the intergrity of the posterior wall. Posterior wall mucosa was closed with vicryl. Anterior gastrostomy was closed in two layers with 3-0 mersilk (Fig. 2). Patient had an uneventful postoperative recovery. Histology of the 10 x 5 x 3 cm. firm, flesh, greyish white tumour (Fig. 3) was reported as low grade gastrointestinal stromal tumour.
GISTs can be divided into four major categories on the basis of their phenotypical features.
1. Tumours showing differentiation towards smooth muscle cells, as evidenced immunohistochemically by the expression of smooth muscle actin and desmin and ultrastructurally by the presence of pinocytotic vesicles, subplamalemmal dense patches and cytoplasmic microfilaments with focal densities. This tumour constitutes the largest category.
Fig. 1 Showing endoscopic appearance of tumour.
Fig. 2 Intra-Operative appearance of the tumour.
2. Tumours showing differentiation towards neural elements, determined by presence on ultrastructural examination of neuron-like features. Occasionally, neuron-specific enolase and/or S-100 protein may be detected on immunohistochemistry.
3. Tumours showing dual differentiation towards smooth muscle and neural elements.
4. Tumours lacking differentiation towards either cell type.
The issue of practical importance in these tumours is the determination of malignancy. Predictors of benign or malignant nature of tumour depends on the tumour size and combination of mitotic activity.
1. Benign : Tumour size less than 5 cm and mitotic count less than 5 x 50/HPF.
2. Borderline : Tumour size greater than 5 cm and mitotic count less than 5 x 50/HPF.
3. Malignant : Tumour of any size and mitotic count of more than 5 x 50/HPF.
Majority of GISTs are seen in adults, however cases have been reported in children also.
The commonest presenting symptoms are abdominal pain and melaena.
Fig. 3 Gross Specimen as seen after excision.
In terms of location, most clinically apparent GISTs are located in pars media (40%) of the stomach followed by the antrum (25%) and in the pylorus (20%). About 60% of the tumours are submucosal and grow towards the lumen, as was noted in the presented case, and about 30% are subserosal and the rest 10% are intramural. The investigation of choice is upper GI endoscopy and barium study of upper GIT. Endosonography can help in determining the exact extent of the tumour within the wall of the organ and extraserosal spread.
The treatment of choice is excision of tumour with the good margin of normal tissue, as was done in the presented case. Simple enucleation of the tumour is discouraged. Wide resection of lymph nodes is not indicated because of the extreme rarity of lymph node metastases. The most common site of metastases of malignant GISTs are the liver, peritoneum and lungs.
1. Stromal tumours. In:Juan Rosai MD eds-Ackermanís Surgical Pathology-8th Ed, Gastrointestinal Tract. 11:645-47.