World J Oncol

World Journal of Oncology, ISSN 1920-4531 print, 1920-454X online, Open Access

Article copyright, the authors; Journal compilation copyright, World J Oncol and Elmer Press Inc

Journal website http://www.wjon.org

Case Report

Volume 7, Number 2-3, June 2016, pages 45-50

Malignant Retroperitoneal Extra-Gastrointestinal Stromal Tumor: A Unique Entity

Figure 1. Color Doppler images of the mass (*) in the retroperitoneum. (a) Extent of the mass anterior to the inferior cava (IVC) with minimal color flow within it (white bold arrow). (b) The hypoechoic mass (*) compressing and splaying the celiac axis (CA) at its origin from the aorta (AO). The common hepatic artery (CHA) is also seen being splayed by the mass. The splenic artery (SA) and the splenic vein (SV) are in close proximity to the mass but appear spared.

Figure 2. Dynamic contrast-enhanced CT (CECT) scan to determine extent of mass with vascular and neighboring structures involvement. (a) CECT in the arterial phase showing the soft tissue retroperitoneal mass (*) (bottom black arrow) anterior to the aorta (bold arrow) splaying and encasing the common hepatic artery (top black arrow). (b) Sagittal maximum intensity projection (MIP) reformatted image of the mass (*) splaying the celiac axis and superior mesenteric artery (SMA) at origin (arrow). (c) Portal venous phase of the dynamic CECT showing mass (*) displacing portal vein (bold arrow) anteriorly with areas of necrosis (#) within it. (d) Coronal reformat showing the mass (*) extending across the midline of the abdomen (arrow).

Figure 3. Photomicrographs. (a) Fine needle aspiration cytology showing fragments of tumor composed of spindle to polygonal shaped cells and elongated vesicular to hyperchromatic nuclei. (b) Cell block showing spindle cell tumor having elongated vesicular nuclei with irregular nuclear borders and prominent nucleoli. (c) Immune-histochemical staining with CD117 (kit) shows positive staining in tumor cells.

**Table 1.** Comparison of Characteristics of Extraintestinal Gastrointestinal Tumors (EGIST and Gastrointestinal Tumor (GIST)
Characteristics	EGIST	GIST
BCL-2: B-cell lymphoma 2.
Age and gender	Usually younger age group 30 - 50 years, median age 58 years, slight female preponderance (M/F: 1:1.014) [12, 13]	Mean age: 55 - 60 years, male/female: 1:1.35 [1]
Clinical presentation	Usually silent in retroperitoneal variety till adjacent structures are compressed	Intra-luminal tumors erode mucosa often present as GI bleed, bowel dilatation, vomiting, exophytic tumors may be silent clinically till necrosis and fistula formation occurs
Location	Omentum, mesentery, liver, pancreas, pelvis (80%), retroperitoneum (20%) [14]	Gastrointestinal tract from esophagus to anus (mc. in stomach (60-70%) followed by small bowel (20-30%) [4]
Radiological findings	Large soft tissue enhancing mass with areas of necrosis, hemorrhage cystic spaces and rarely calcification [15]	Exophytic soft tissue mass projecting outside or inside the gastrointestinal lumen with ulceration and fistulous track formation , bowel dilation, ascites and omental caking [5, 16]
Histopathology	Spindle cell type, epithelioid type [17]	Spindle (70%), epithelioid (20%), mixed (< 10%) type [7, 16]
Immunohistochemistry	Positive staining for CD117 for confirmation. Staining for other immunological markers is variable: BCL-2 (80%), CD34 (70%), smooth muscle actin (35%), S100 (10%), and desmin (5%) [17]
Disease spread/metastasis	Direct spread into the peritoneum and retroperitoneum	Peritoneum, liver
General pathologic consensus for grading and prognosis	None devised so far	Standard consensus available based on tumor size and mitotic count [18]
Differential diagnosis on imaging [7]	Lymphoma Sarcoma/mesenchymal tumor of the involved organ such as malignant fibrous histiocytoma, liposarcoma, leiomyosarcoma, fibrosarcoma	Adenocarcinomas of the bowel [5]
Management	Surgical resection/imatinib therapy [12]	Complete surgical resection for non-metastatic disease followed by imatinib as adjuvant therapy
Prognosis	Worse than GIST , usually more aggressive [13]	Long-term recurrence seen, only 10% free of disease at 10 years

Table 1. Comparison of Characteristics of Extraintestinal Gastrointestinal Tumors (EGIST and Gastrointestinal Tumor (GIST)

Characteristics

EGIST

GIST

BCL-2: B-cell lymphoma 2.

Age and gender

Usually younger age group 30 - 50 years, median age 58 years, slight female preponderance (M/F: 1:1.014) [12, 13]

Mean age: 55 - 60 years, male/female: 1:1.35 [1]

Clinical presentation

Usually silent in retroperitoneal variety till adjacent structures are compressed

Intra-luminal tumors erode mucosa often present as GI bleed, bowel dilatation, vomiting, exophytic tumors may be silent clinically till necrosis and fistula formation occurs

Location

Omentum, mesentery, liver, pancreas, pelvis (80%), retroperitoneum (20%) [14]

Gastrointestinal tract from esophagus to anus (mc. in stomach (60-70%) followed by small bowel (20-30%) [4]

Radiological findings

Large soft tissue enhancing mass with areas of necrosis, hemorrhage cystic spaces and rarely calcification [15]

Exophytic soft tissue mass projecting outside or inside the gastrointestinal lumen with ulceration and fistulous track formation , bowel dilation, ascites and omental caking [5, 16]

Histopathology

Spindle cell type, epithelioid type [17]

Spindle (70%), epithelioid (20%), mixed (< 10%) type [7, 16]

Immunohistochemistry

Positive staining for CD117 for confirmation. Staining for other immunological markers is variable: BCL-2 (80%), CD34 (70%), smooth muscle actin (35%), S100 (10%), and desmin (5%) [17]

Disease spread/metastasis

Direct spread into the peritoneum and retroperitoneum

Peritoneum, liver

General pathologic consensus for grading and prognosis

None devised so far

Standard consensus available based on tumor size and mitotic count [18]

Differential diagnosis on imaging [7]

Lymphoma
Sarcoma/mesenchymal tumor of the involved organ such as malignant fibrous histiocytoma, liposarcoma, leiomyosarcoma, fibrosarcoma

Adenocarcinomas of the bowel [5]

Management

Surgical resection/imatinib therapy [12]

Complete surgical resection for non-metastatic disease followed by imatinib as adjuvant therapy

Prognosis

Worse than GIST , usually more aggressive [13]

Long-term recurrence seen, only 10% free of disease at 10 years