CASE REPORT

Malignant gastroin-
testinal stromal cell

tumour (GIST) of
the stomach

W Spies
MSChS

C S de Vries
MMedRad(D)

Department of Diagnostic Radiology
University of the Free State

Bloemfontein

Case
presentation

A 55-year-old female patient pre-
sented with a painful mass in the left
hypochondrium.

Sonar revealed a well-demarcated
round thin-walled lesion with internal
echoes with a homogeneous pattern
(Fig. I). The mass measured approxi-
mately 15 x 13 cm. Duplex Doppler
revealed a low venous flow pattern,
and a sonar-guided fine needle aspira-
tion (FNA), revealed a bloody aspirate
(Fig. 2). Computerised tomography
(CT) was done immediately after
ultrasound investigation. No oral con-
trast was given. The cystic lesion
(Hounsfield unit (HU) = 18 on pre-
contrast study) was situated adjacent
to the stomach in the lesser omental
sac. It was difficult to differentiate the
cystic lesion from either the stomach
or the pancreas on CT. The splenic
artery could also not be differentiated
from the cystic lesion. The post-con-
.trast CT showed rim enhancement,

Fig. 1. Sonar of a thin-walled lesion with internal
echoes.

Fig. 2. Duplex Doppler revealing low venous flow
peNem.

Fig. 3, Pre-contrast CT.

but no enhancement of the contents
was apparent (Figs 3 and 4).

31 SA JOURNAL OF RADIOLOGY • June 2002

Fig. 4, Post-contrast CT.

The preliminary differential diag-
nosis included a haemorrhagic
pseudocyst, thrombosed splenic
artery aneurysm, subacute
haematoma, or abscess. A splenic,
hepatic and superior mesenteric
artery (SMA) angiogram revealed no
significant pathology, splenic artery
aneurysm, or neovascularity. A surgi-
cal exploration and resection was then
done. Stomach wall slices showed the
presence of a cellular tumour with
small areas of necrosis. Evidence of
spindle-shaped and epithelioid cells
was found. A slight pleomorphism
was present with an average of 2 mito-
sis per 10 high-field magnification.

The final diagnosis was a malig-
nant gastrointestinal stromal cell
tumour (GIST).

Discussion
GISTs are uncommon mesenchy-

mal tumours of the gastrointestinal
(GI) tract. GISTs include tumours
previously designated as leiomyoma,
cellular leiomyoma, leiomyoblastoma
and leiomyosarcoma. The oesophagus
is the exception, with leiomyoma the
most common mesenchymal tumour.
Studies show that phenotypically
undifferentiated GISTs are also genet-
ically different from leiomyomas and
schwannomas and support their das-



CASE REPORT

sification apart from leiomyornas.'
GISTs are composed of spindle (70%)
or epithelioid (30%) cells. 10 - 30%
are malignant, showing intra-abdom-
inal spread and/or liver metastasis.

GISTs are both malignant and
benign. They may be submucosal,
subserosal or intraluminal. The CT
appearance of a GIST may include a
sharply defined mass with homoge-
neous attenuation, sometimes with
clarification.

A study by Kim et al? analysed the
clinical presentation, pathology and
long-term follow-up of 19 patients
with GIST tumours (12 gastric, 2 duo-
denal, 3 jejunal and 2 rectal). The
most common clinical presentation
was GI bleeding. CT, contrast studies,
and endoscopy were used to identify
tumour mass. In only two instances
could the diagnosis of GIST be made
preoperatively.

Histology was variable and the size
of the tumours ranged from 0.8 to
23 em. The clinical course is
favourable with complete resection.

Needle biopsy can be used for the
diagnosis of GIST tumours preopera-
tively. GIST can be classified as
benign, borderline, or malignant
using immunochemistry, size, mitotic
activity and clinical outcome. Spindle
cell and epithelioid types can be dis-
tinguished. Cytomorphology alone
cannot be used to assess malignancy
and predictions of aggressiveness but
must be interpreted with a gross and
histological examination of the resect-
ed specimen. Immunocytochemical
staining for CD is helpful in confirm-
ing the diagnosis. Care must be taken
to differentiate epithelioid-type GISTs
from adenocarcinoma. GISTs are also
immunohistochernically positive for
C-kit (CDl17), CD34 and sometimes

for actin, but are mostly negative for
desmin and S-l 00 protein. The malig-
nant GIST especially,shows activating
mutations in the C-kit gene. GIST and
GI autonomic nerve tumours
(GANTs) can overlap. The cell of ori-
gin is not well understood, but resem-
blance to the interstitial cells of Gajal,
expression of the smooth muscle
markers and occurrence outside of
the GI tract suggest an origin from
multipotential cells that can differen-
tiate into Cajal and smooth muscle
cells.

References
1. Dodd LG, Nelson RC, Mooney EE, Gottfried

M. Fine-needle aspiration of gastrointestinal
stromal tumours. Am] Clin Patho/199B; 109:
439-443.

2. Kim CJ, Day S,YehKA.Gastrointestinal stromal
tumours: analysis of clinical and pathologic fac-
tors. Am Surg2001; 67: 135-137.

32 SA JOURNAL OF RADIOLOGY'. June 2002