2019, Volume 35, Number 2, Page(s) 151-156
Inflammatory Myofibroblastic Tumor of the Stomach Presenting as an Exophytic Mass - A Diagnostic Dilemma
Meena JADHAV, Rekha HARVI, Rashmi PATIL, Shreekant KITTUR
Department of Pathology, Belgaum Institute of Medical Sciences, BELGAVI, INDIA
Keywords: Inflammatory myofibroblastic tumor, Inflammatory pseudotumor, Stomach
Inflammatory myofibroblastic tumor is an uncommon soft tissue neoplasm of uncertain biologic behavior, and rarely reported in the
stomach. An eighteen-year-old male presented with a mass in the epigastrium of three-month duration. Clinical and radiological examination
suggested a gastrointestinal stromal tumor or a leiomyoma in the lesser curvature of the stomach. On the basis of histomorphological features
and immunohistochemical analysis the diagnosis of inflammatory myofibroblastic tumor in the lesser curvature of the stomach was made.
Inflammatory myofibroblastic tumor should be considered in the differential diagnosis of soft tissue tumors of the stomach.
Inflammatory myofibroblastic tumors (IMTs) are
distinctive mesenchymal neoplasms of intermediate
biologic potential that are composed of myofibroblastic
spindle cells accompanied by an inflammatory infiltrate
of plasma cells, lymphocytes and eosinophils1
. The first
IMT was reported in the lungs, in 19372
extrapulmonary sites are mesentery, omentum, liver,
urinary bladder and retroperitoneum. The tumor shows
tendency for local invasion, recurrence, multicentricity and
. IMTs are rarely reported in the stomach4-7
They are usually misdiagnosed clinically and radiologically
and pose a diagnostic dilemma even on histopathological
examination, which is why we presented this case.
An eighteen-year-old male patient presented with a mass in
the epigastrium, loss of appetite and loss of weight of threemonth
duration. There was no history of fever, vomiting
or hematemesis. On physical examination, the patient
was pale and abdominal palpation revealed a firm mass of
9 x 7 cm size in the epigastrium and mild hepatomegaly.
Hematological investigations revealed hemoglobin level
of 8.6 g/dl, erythrocyte sedimentation rate of 60mm/first
hour, normal platelet count and microcytic hypochromic
anemia. The patient was nonreactive for HIV I and II
antibodies. The liver function tests were within normal
Esophagogastroduodenoscopy showed a smooth hemispherical
mass in the lesser curvature of the stomach, just
below the esophagogastric junction with normal overlying
mucosa. A presumptive diagnosis of gastric leiomyoma
was made (Figure 1A). The biopsy taken at that time
was inconclusive. Computed tomography (CT) scan of
the abdomen revealed a large, well defined, thick-walled
peripherally-enhancing soft tissue mass of 8.6 x 7.7 x 6.8 cm
size in the lesser curvature of the stomach (Figure 1B). The
liver was enlarged, showed homogenous density without
any space-occupying lesion. Radiological impression was
gastrointestinal stromal tumor (GIST). Ultrasound guided
FNAC suggested gastric leiomyoma or GIST.
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|Figure 1: A) Endoscopic image showing the gastric mass. B) CT scan showing soft tissue lesion arising from the wall of the stomach.
C) Gross photograph of the mass with shiny outer surface and whorled, mucoid cut surface.
At operation, the mass was exophytic, attached to the
lesser curvature of the stomach with a narrow base, and
compressing the gastric lumen without invading adjacent
structures. There was no regional lymphadenopathy or
ascites. The liver was enlarged. No remarkable pathology
was observed in the other organs. The mass was excised.
On gross examination, the mass was capsulated, measured
9 x 9 x 7 cm with a shiny outer surface and yellowish white,
whorled, mucoid cut surface (Figure 1C).
Microscopic examination showed that the tumor was arising
from the muscular layer, composed of mildly pleomorphic,
spindle to stellate cells arranged singly and in fascicle,s
in a background of myxoid, edematous stroma with
inflammatory infiltrate of plasma cells and lymphocytes (Figure 2A,B). The tumor cells had eosinophilic cytoplasm
with fusiform nuclei, fine chromatin with tapered to blunt
ends, and prominent eosinophilic nucleoli. Mitoses were
1-2/10 HPF. There was no calcification or necrosis. No
gastric mucosa could be identified. The surgical margins
showed presence of tumor. On immunohistochemistry
(IHC) the tumor cells were strongly positive for SMA, MSA
(Figure 2C,D), but negative for CD117 (c-KIT), DOG1,
CD34, ALK-1, caldesmon, desmin (Figure 3A-F), betacatenin,
S-100 protein, CK and EMA.
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|Figure 2: A,B) Atypical spindle cells in an edematous stroma with plasmacytic and lymphocytic infiltration (H&E; x400). C) Tumor
cells are immunopositive for SMA (x200) and D) MSA (x200).
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|Figure 3: Microphotograph showing tumor cells negative for A) CD117 (x200), B) DOG1 (x200), C) CD34 (x200), D) ALK-1 (x200),
E) Caldesmon (x200) and F) Desmin (x200).
Based on the above information, a diagnosis of IMT in
lesser curvature of the stomach was rendered. The patient is doing well without any evidence of disease, five years
Inflammatory myofibroblastic tumor (IMT) has been
named as inflammatory pseudotumor, inflammatory
myofibroblastic proliferation, plasma cell granuloma
or inflammatory myofibroblastoma4
. Now it is
classified under intermediate neoplasms in World Health
Organization, Histological Typing of Soft Tissue Tumors8
. It is rare in the gastrointestinal tract, with ileocaecal
region and stomach as the common sites9
. There are about 34 gastric IMT cases reported in the English literature.
The clinicopathological features of these 34 cases are
summarized in Table I2,4-7,10-13
. The age at diagnosis
ranged from 4 months to 80 years (mean 27.2 years).
Females were more commonly affected than males. The
common symptoms were abdominal pain and abdominal
mass. The mean tumor size was 6.9 cm. In the stomach,
IMT was frequently reported in the body of the stomach
but involvement of lesser curvature with exophytic mass
formation was rare4,7
. Follow up data was available in
26 cases with duration of follow up time ranging from 1
month to 14 years (mean 2.7 years). Recurrence was seen in
4 cases out of 26 cases reviewed in the literature.
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|Table I: Clinicopathological features of 34 previously reported cases of gastric IMTs
The etiology of IMT is unknown2,4,6. The various
mechanisms postulated were secondary to trauma,
surgery, immunological diseases or infections like
mycobacteria, Epstein-Barr virus, actinomycetes, Nocardia
and Helicobacter pylori9. In the present case, there was
no past history of serious illness, trauma, gastritis, gastric
endoscopy or biopsy. Recent studies have demonstrated
clonal cytogenetic aberrations with rearrangement of
ALK gene on chromosome 2p23 in 50% to 70% of cases,
suggesting a neoplastic origin for IMT1.
The present case of IMT, posed a diagnostic dilemma in
differentiating it from GIST and inflammatory fibroid
polyp (IFP). GISTs typically do not show inflammatory background as is seen in IMTs. They frequently show
skeinoid fibers that were not seen in the present case. On
IHC the GISTs are strongly positive for CD117, DOG1
and CD34 but negative for ALK-1 whereas IMT shows an
opposite profile. In the present case, the tumor cells were
negative for CD117, DOG1 and CD34. They were strongly
positive for SMA, MSA but negative for ALK-1, caldesmon
and desmin hence favoring a diagnosis of IMT over
GIST. Though ALK positivity is helpful in the diagnosis
of IMT, it is only seen in 56% of the cases. ALK negative
IMTs are said to be associated with the presence of greater
pleomorphism, atypical mitosis and distant metastasis, but not local recurrence1. The present case did not show
atypical mitosis and there is no evidence of metastasis five
years after surgery. Inflammatory fibroid polyps (IFP)
are typically submucosal and show granulation tissue like
stroma and eosinophil rich infiltrate with perivascular
cuffing contrary to IMTs that show less eosinophils and
more lymphocytes. Most of these lesions show spindle
cells positive for CD34, whereas tumor cells of IMTs are
negative for CD34 and positive for actins. The present case
did not show eosinophils or perivascular cuffing and tumor
cells were negative for CD34.
Other differential diagnoses considered were leiomyoma,
polyps with bizarre stromal cells, solitary fibrous tumor,
fibromatosis, peripheral nerve sheath tumor and follicular
dendritic sarcoma but were excluded based on the routine
microscopic and IHC findings. Inflammatory fibrosarcoma
may be related to IMT, as it shares similar clinical and
There are no definite clinical, microscopic or genetic
features to predict the recurrence or metastasis1. They
may undergo spontaneous regression8. Gastric IMTs
have relatively good prognosis as the recurrence rate is 15%
to 37% within a year after surgery7. Complete surgical
excision is the treatment of choice with long-term follow-up2,4,9. Chemotherapy and radiotherapy are advocated for
cases with recurrence or metastasis1. To conclude, IMT
have a relatively good prognosis, and should be considered
in the differential diagnosis of soft tissue tumors in the
stomach to avoid unnecessary aggressive therapy.
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