CASE 9728 Published on 27.03.2012

Widespread metastatic abdominal GIST

Section

Abdominal imaging

Case Type

Clinical Cases

Authors

Scalise P, Angelini G, Pancrazi F, Aringhieri G, Accogli S, Lauretti D, Ginanni B, Bemi P, Neri E, Bartolozzi C.

Department of Diagnostic and Interventional Radiology,
University Hospital of Pisa, Italy
Patient

46 years, male

Categories
Area of Interest Abdomen ; Imaging Technique CT
Clinical History
A 46-year-old male patient came to the emergency department complaining of vomiting, cramping abdominal pain, constipation with bowel closed to feces and gas.
As the patient’s clinical history included repeated episodes of intestinal sub-occlusion, bowel obstruction was suspected and an emergency Computed Tomography (CT) evaluation was performed.
Imaging Findings
Emergency CT examination (Fig. 1) showed a voluminous space-occupying solid formation located in left hemiabdomen, mesogastrium and pelvis, extending from superior pole of spleen to pelvic cavity.
After contrast medium administration the mass appeared dishomogeneous; it compressed and dislocated adjacent anatomical structures, globally enclosing and incorporating left descending/sigmoid colon.
Multiple clusters of peritoneal carcinomatosis and pelvic effusion were also depicted.
At CT colonography (Fig. 2), no stenosing or obstructing endoluminal masses were depicted; colic lumen seemed to be extrinsically reduced by the endoperitoneal mass.
Because the lesion origin was uncertain, patient underwent explorative laparotomy: an affected ileal loop was removed and multiple biopsies were performed.
At immunohistochemical cell-staining, the biopsy specimens were positive for CD117/CD34. The gross lesion was characterised as peritoneal metastasis of gastrointestinal stromal tumour (GIST) with high mitotic-index, departing from small intestine.
Given lesion dimensions, neoadjuvant therapy (Imatinib) was administered to attempt a tumour-size reduction; follow-up CT examinations (Fig. 3-4) showed an increase of tumour dimensions. Actually the patient is under evaluation for alternative chemotherapy treatment suitability.
Discussion
GISTs are rare but they are the commonest non-epithelial neoplasms of gastrointestinal (GI)-tract, defined as tyrosine-kinase-receptor (KIT)-positive mesenchymal spindle-or-epithelioid-cell neoplasms occurring primary in the GI-tract, omentum, or mesentery [1].

Pathogenesis is related to gain-of-function mutations in c-kit oncogene (CD117) resulting in constitutive activation of KIT, which is used as immunohistochemical-marker for diagnosis [2]. CD34, SMA, S100 and Desmin proteins might also be expressed [1].
Histological origin has been classically attributed to smooth-muscle cell [1], but mutation of Cajal cells has also been proposed [1].

90% of GISTs occur in adults (median age: 63 years) most commonly in stomach (50-60%) and small intestine (30%-40%), but they might arise everywhere along the GI-tract or be even extra-gastrointestinal [2].

Clinical presentation depends on tumour size/localisation and is frequently nonspecific (nausea, vomiting, sense of fullness, abdominal discomfort or pain, weight loss); bleeding or abdominal organs displacement are common in case of large masses with extraluminal growth arising from gastrointestinal wall.

50% of patients present metastases at diagnosis given GISTs highly tendency to seed.
Distant metastases occur in case of peritoneal, omental, mesenterial or hepatic location due to haematogenous spread; lymph node metastases are rare [2].

Contrast–enhanced CT is the gold standard for diagnosis, treatment-effects evaluation and early detection of recurrence [3]. GISTs appear as endo-exophytic masses whose contrast-enhancement depends on size: smaller lesions are relatively homogeneous and well-defined; larger lesions (5-8 cm) show less-defined margins, inhomogeneous density, combined intraluminal/extraluminal growth and tendency to spread.

GISTs always have a malignant potential and no lesion might be definitely labelled as benign [2-3].
Size and mitotic count are the most useful predictors of malignant behaviour [2]: generally tumours >5cm are considered malignant while <5cm are associated with a low risk of recurrence. Signs of malignancy include large volume, irregular surface, not-well-defined margins, inhomogeneous enhancement, GI wall infiltration, liver (65%) or peritoneal (50%) metastasis [4].
Metastatic lesions are enhancing masses with heterogeneous areas due to necrosis, haemorrhage or cystic degeneration, similarly to primary tumours [2-4].

Complete surgical resection represents GISTs gold-standard therapy.
Location and tumour-size are more reliable prognostic factors than negative surgical margins; risk of recurrence is higher during the first 3-5 years after surgery [2].
In case of GISTs metastasis, recurrence or unresectable lesions, molecular-targeted therapy with Imatinib-mesylate (c-KIT tyrosine-kinase-receptor selective-inhibitor) is actually considered the first-line adjuvant/neoadjuvant treatment [2, 5, 6].
Some patients do not respond to Imatinib or present an aggravation during therapy: resistent lesions appear as growing nodules in the tumour, as in our case [2].
In these cases, surgical resection is questionable [6] and second-generation tyrosine-kinase inhibitors as Sunitinib might serve as alternative therapies [7].
Differential Diagnosis List
Peritoneal metastasis of high mitotic-index GIST departing from small intestine.
Neuroendocrine tumours
Leiomyoma/Leiomyosarcoma
Schwannoma
Lymphoma
Adenocarcinoma
Final Diagnosis
Peritoneal metastasis of high mitotic-index GIST departing from small intestine.
Case information
URL: https://www.eurorad.org/case/9728
DOI: 10.1594/EURORAD/CASE.9728
ISSN: 1563-4086

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