|Year : 2012 | Volume
| Issue : 1 | Page : 51-53
Massive gastrointestinal stromal tumor of stomach mimicking a uterine leiomyoma
Keyur S Gutte
Department of Surgical Oncology, Noble Hospital, Pune, Maharashtra, India
|Date of Web Publication||20-Jun-2012|
Keyur S Gutte
Consultant Surgical Oncologist, 402, Saffron, Gulmohar City, Kharadi, Pune - 411 014, Maharashtra
Source of Support: None, Conflict of Interest: None
Gastrointestinal stromal tumors (GISTs) are a rare group of non-epithelial tumors of the gastrointestinal tract and represent less than 1% of all primary gastric tumors. This case report is of a 45-year-old female patient who presented with a lump in the right lower abdomen extending inferiorly into the pelvis. Clinical and radiological findings were suggestive of a large intraperitoneal pelvic mesenchymal tumor or a pedunculated uterine leiomyoma. At laparotomy, the tumor was found arising from lesser curvature of stomach. Complete excision was done and immunohistochemistry confirmed the diagnosis of a GIST. The patient is presently asymptomatic at 4 years and is being kept under surveillance. Gastric GISTs should be locally excised with macroscopically clear margins, allowing subsequent symptomatic follow up without the need for adjuvant therapy, which may be reserved for recurrences if further surgery is deemed inappropriate.
Keywords: Gastrointestinal stromal tumor, Imatinib, recurrence
|How to cite this article:|
Gutte KS. Massive gastrointestinal stromal tumor of stomach mimicking a uterine leiomyoma. Med J DY Patil Univ 2012;5:51-3
| Introduction|| |
Gastrointestinal stromal tumors (GISTs) are a rare group of non epithelial tumors that can be found at all levels of the gastrointestinal tract and represent less than 1% of all primary gastric tumors and less than 3% of all gastrointestinal tumors. ,
60-70% of GISTs are found in the stomach, 25-35% in the small intestine, about 5% in the colon, rectum and appendix, and 3% in the esophagus.  GISTs are commonly diagnosed in the fifth to seventh decades; they are unusual in patients under the age of 40. 
The cell of origin of these tumors is thought to be the interstitial cell of Cajal, which is responsible for the motility of the gastrointestinal tract.  The diagnosis of GISTs has become more precise with the introduction of immunohistochemistry to identify the expression of the transmembrane tyrosine kinase receptor codified by the c-kit proto oncogene. The prevalence of mutations in the c-kit proto oncogene is 70-80%, which leads to malignant transformation. Between 10% and 30% GISTs behave in a malignant manner. Various classifications have been proposed to identify malignant potential based on tumor size, mitotic index, and presence of necrosis, infiltration of adjacent structures, and presence of lymph node metastasis.  A number of different treatments have been postulated for the management of gastric GISTs. Some have advocated radical resection followed by surveillance with serial endoscopies and regular post operative imaging. ,,
Chemo radiotherapy regimens are now largely outdated since the advent of an effective medical therapy in the anti c-kit antibody Imatinib, approved by the FDA in 2001.
| Case Report|| |
A 45-year-old female presented with a lump in the right lower abdomen, associated with dull pain, post prandial fullness, increase in frequency of micturition, but no bowel or menstrual irregularity. She had a family history of neurofibromatosis. Clinical examination revealed pallor, a firm slightly tender mass (20 × 15 cm) in the right lower abdomen extending inferiorly into the pelvis.
Hematological investigations showed anemia (Hemoglobin - 8.7 gm%). CA-125 levels were normal. CT of the abdomen revealed a single large mass occupying the right lower abdomen suggestive of either a large mesenchymal tumor or a pedunculated uterine leiomyoma [Figure 1].
At laparotomy, a well-encapsulated mass (21 × 16 × 9 cm) was found arising from the serosa of the lesser curvature of stomach with blood supply from the left and right gastric vessels. The uterus, ovaries, Fallopian tube More Detailss, and rest of the abdomen including the liver was normal. Complete excision of this mass was done, keeping the capsule intact and without sacrificing any portion of the stomach [Figure 2].
Histopathology showed neoplastic spindle cells arranged compactly with no necrosis and rare mitoses, suggesting a low grade spindle cell tumor. Immunohistochemistry confirmed the diagnosis of a GIST (c-kit and Vimentin positive; Smooth Muscle Actin, Desmin and S-100 negative). Owing to its size (more than 5 cm) and number of mitosis (5-10/50 high power fields), it was classified as "potentially malignant."
The patient made a good post operative recovery and is free from recurrence or metastasis at 4 years. Adjuvant Imatinib was not recommended despite the size, in view of complete surgical excision.
| Discussion|| |
The term GIST was accepted in the WHO International Classification of Tumors in 1990. Prior to clarification in the diagnosis of GISTs, they were often classified alongside leiomyosarcomas and other connective tissue and neural malignancies.
Pain is present in 40-70% of cases, hemorrhage occurs in 20-50% of cases, and the tumors are palpable in 20% of cases. Only 10% of these tumors are malignant and these are characterized by exophytic and heterogeneous patterns and areas of necrosis. Histologically, 70% GISTs are spindle celled, 30% are epithelioid, and less than 1% are both spindle celled and epithelioid. These latter tumors are more malignant and their prognosis is worse.
Gastric tumors that are more proximally located, less than 5 cm in diameter and have fewer than 5 mitoses per 50 high power fields - are considered low risk. Borderline cases are those with 5-10 mitoses per 50 high power fields. High-risk patients are those with disseminated and/or distally located tumors that are more than 5 cm in diameter and have more than 10 mitoses per 50 high power fields.  The Kit protein, the transmembrane receptor with protein kinase activity identified by the monoclonal antibody CD117 is expressed by these tumors. The gene that codifies the expression of the Kit protein is c-kit, a proto oncogene located on chromosome 4 (4q11-12). Other tumors with this pattern are malignant melanoma, endometrial carcinoma, dysgerminoma, and mast cell neoplasia.
ST1571 (Imatinib mesylate) is an oral agent that selectively inhibits the tyrosine kinase kit receptor, active in most GISTs, with the maximum efficiency and minimal side effects. The recommended dose is 400 mg/day with a maximum up to 800 mg/day. Primary resistance is seen in 10-15% patients.
Treatment of these tumors basically involves radical surgery of the primary lesion, or debulking of large lesions followed by adjuvant Imatinib mesylate. Provided complete resection (R0) has been achieved, symptomatic follow up is sufficient owing to the indolent nature of most tumors. In the event of a recurrent GIST, therapeutic potions include further surgical resection and/or adjuvant Imatinib therapy.
For GISTs resistant to Imatinib, when intraperitoneal dissemination is observed, topical intraperitoneal mitoxantrone may be used after maximal surgical excision. Another possible treatment is embolization of the hepatic artery for painful hepatic metastasis or for those cases with a high risk of hemorrhage.
The current survival rates of patients with advanced GISTs treated with surgery and Imatinib mesylate are as follows - total response: 59%, stable illness: 26%, and tumor progression: 13%. These response rates are significant improvements, especially considering that, prior to introduction of Imatinib, the progression of metastatic GISTs was 100%. However, most of these studies are still at the early follow up stage, thus longer follow up is necessary. 
| References|| |
|1.||Miettinen M, Sarlomo Rikala M, Lasota J. Gastrointestinal Stromal Tumours: Recent advances in understanding of their biology. Hum Pathol 1999;30:1213-20. |
|2.||Miettinen M, Lasota J. Gastrointestinal Stromal Tumours (GISTs): Definition, occurrence, pathology, differential diagnosis and molecular genetics. Pol J Pathol 2003;54:3-24. |
|3.||Sircar K, Hewlett BR, Huizinga JD, Chorneyko K, Berezin I, Riddell RH. Interstitial cells of Cajal as precursors of gastrointestinal stromal tumours. Am J Surg Pathol 1999;23:377-89. |
|4.||Butcher P, Taylor S, Villiger P, Morel P, Brundler MA. Are there any prognostic factors for small intestinal stromal tumours? Am J Surg 2004;187:761-6. |
|5.||Knoop M, St Friedrichs K, Dierschke J. Surgical management of gastrointestinal stromal tumours of the stomach. Langenbecks Arch Surg 2000;385:194-8. |
|6.||Besana-Ciani I, Boni L, Dionigi G, Benevento A, Dionigi R. Outcome and long term results of surgical resection of gastrointestinal stromal tumours (GIST). Scand J Surg 2003;92:195-9. |
|7.||Samiian L, Weaver M, Velanovich V. Evaluation of gastrointestinal stromal tumours for reccurence rates and patterns of long term follow up. Am J Surg 2004;70:187-91. |
|8.||Ray-Coquard I, Le Cesne A, Michallet V, Boukonivas I, Ranchere I, Thiesse P, et al. Gastrointestinal stromal tumours: News and comments. Bull Cancer 2003;90:69-76. |
|9.||DeMatteo RP. The GIST of targeted cancer therapy: A Tumour (Gastrointestinal stromal tumour), a mutated gene (c-kit) and a molecular inhibitor (ST1571). Ann Surg Oncol 2003;9:831-9. |
[Figure 1], [Figure 2]