|Ahead of print
Primary retroperitoneal GIST: Case report and review of literature
Krunal H Khobragade1, Shraddha Patkar1, Mahesh Goel1, Ayushi Sahay2
1 Department of Surgical Oncology, Tata Memorial Hospital, Mumbai, Maharashtra, India
2 Department of Pathology, Tata Memorial Hospital, Mumbai, Maharashtra, India
|Date of Submission||22-Aug-2018|
|Date of Decision||11-Nov-2018|
|Date of Acceptance||03-Dec-2018|
|Date of Web Publication||08-Jul-2020|
Krunal H Khobragade,
Department of Surgical Oncology, Tata Memorial Hospital, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
Extraintestinal gastrointestinal stromal tumors (EGISTs) are mesenchymal tumor with no connection to tubular gastrointestinal system. They commonly arise from omentum and mesentry. Retroperitoneum is a rare primary site. We herein report a case of a 33 year old woman who underwent upfront surgery for primary retroperitoneal gastrointestinal stromal tumor and is now disease-free on adjuvant Imatinib.
Keywords: Extraintestinal gastrointestinal stromal tumors, retroperitoneum, Imatinib
| » Introduction|| |
Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. Approximately, 60% arise in the stomach and 30% arise in the small bowel; the other 10% arise in the esophagus, colon, rectum, gallbladder, appendix, omentum, mesentery, retroperitoneum, and pelvis. GISTs that are not connected to the walls or serosal surfaces of gastrointestinal tubular organs are called extraintestinal GIST (EGIST) and are rare. Most of the EGISTs originate from the omentum and mesentry; however, other primary sites, such as pancreas, hepatobiliary tree, uterus, and vagina have been reported.[3-5] EGISTs of the retroperitoneum are very rare and not much is known about their clinicopathological behavior. Herein, we present a case of EGIST in a 33-year-old woman located in the retroperitoneum with no connection to gastrointestinal system.
| » Case Report|| |
A 33-year-old woman presented to our hospital with pain in right side of abdomen and loss of appetite for 1 year. On examination, she had a 15 × 12 cm hard palpable lump in right hypochondrium and right lumbar region. Abdominal computed tomography (CT) scan showed a 13 × 10 cm heterogenously enhancing retroperitoneal mass with displacement of right colon, duodenum, and right kidney [Figure 1]. The patient underwent ultrasonography-guided biopsy from the mass which showed malignant tumor in a myxoid stroma. Patient underwent surgical exploration. Intraoperatively, there was a 20 cm × 18 cm retroperitoneal mass with involvement of right renal vein. Duodenum and head of pancreas were pushed medially by tumor and there was no communication with gastrointestinal system. The tumor was excised completely (R0 resection) with intact capsule along with right nephrectomy. Postoperative course was uneventful. Pathological examination revealed a 17 × 15 cm encapsulated retroperitoneal tumor with negative margins. The cut surface of tumor was yellowish with solid-cystic areas and myxoid and friable in consistency. On microscopic examination [Figure 2], an encapsulated tumor was seen with spindle and epithelioid cells arranged in sheets and short fascicles. The mitotic count was 1-2/10hpf. Mib-1 labeling index was 5–7% in the highest proliferating areas. On immunohistochemistry, tumor cells were positive for S100 and c-kit while negative for DOG1, SMA, CD34, HMB45, and Melan-A [Figure 3]. SOX 10 was not performed. The nephrectomy specimen did not reveal any malignant involvement. She is on adjuvant imatinib in view of intermediate risk and is disease free at 18 month interval.
| » Discussion|| |
GISTs are potentially malignant tumors and the commonest mesenchymal tumors of the gastrointestinal tract. The age-adjusted incidence of clinical GIST was 0.8 per 100,000 per year. The term gastrointestinal stromal tumor was initially coined as a purely descriptive term by Mazur and Clark in 1983 to define intraabdominal tumors that were not carcinomas (i.e., nonepithelial tumors). The cell of origin for GIST is interstitial cell of Cajal or related stem cell precursor. In 1998, Hirota et al. discovered a gain of function mutation in the protooncogene KIT in GIST. Approximately, 75% of GISTs bear activating mutations in KIT, with PDGFRα mutated in another 10% and the remaining group of “wild type” GISTs has continued to shrink because alterations have been discovered in BRAF, SDH, and NF1 in other patients. Approximately, 95% of GISTs are positive for KIT (CD117) and/or discovered on GIST-1 (DOG1), and 70% are found to be positive for CD34 by immunohistochemistry. The tumor extent is identified on cross-sectional imaging like CT or magnetic resonance imaging.
The term “EGIST” was coined by Reith et al. in 2000 for tumors which occur in soft tissues of the abdomen and described them as histologically and immunophenotypically similar to GISTs. EGIST account for less than 10% of stromal tumors. Most EGISTs arise from omentum, mesentery, retroperitoneum, and other undefined abdominal sites. Till date, only 173 cases of primary retroperitoneal GIST have been reported.[12-14] However, in most cases the location of retroperitoneal GIST is not further specified. In the largest series of 112 cases of retroperitoneal GISTs, 35 were identified to have gastrointestinal communication and in 35 cases the primary site was unspecified. Peripancreatic was the largest group when site was specified in this series. Retroperitoneal GISTs are usually advanced and large in size >10 cm. The two main patterns of histology in retroperitoneal EGISTs are spindle cell and epithelioid. Most retroperitoneal GISTs are c-kit (95%) and DOG 1 (93%) positive. On imaging, they may be confused with lymphomas or other mesenchymal tumors at the same location; however, the differentiation from EGISTs on imaging may be made on the basis of absence of necrosis, cystic changes, hemorrhage, and calcification within lymphomatous neoplasms. The current form of management for these tumors includes surgery and debulking of masses whenever possible along with adjacent tissues which are infiltrated. Imatinib can be used as neoadjuvant therapy if initial surgery involves multiorgan resection. Retroperitoneal GISTs have poorer outcomes compared to classical GISTs, with median survival of 14 months and few surviving beyond 5 years. Operability and mitotic rate have been identified as important prognostic factors.
| » Conclusion|| |
Due to rarity of primary retroperitoneal GIST, it is important to study their imaging, histology, and clinical behavior.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]