Small bowel (small intestine) - Inflammatory myofibroblastic tumor

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Small bowel (small intestine)

Benign tumors and tumor-like conditions

Inflammatory myofibroblastic tumor

Reviewer: Hanni Gulwani, M.D. (see Reviewers page)
Revised: 21 December 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● Also called inflammatory pseudotumor; previously called inflammatory fibrosarcoma
● Often in children but can occur at any age
● No clinical associations
● Benign, but may recur; rarely has malignant behavior
● Rarely behaves malignant
● ALK+ tumors (22% of patients age 40 years or younger) have a more favorable prognosis (Am J Surg Pathol 2001;25:761)
● Complications: obstruction, intussusception

Case reports
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● 2 month old infant with intestinal obstruction (J Med Assoc Thai 2009;92:114)
● 2 year old girl with jejunal tumor (Pathol Int 2001;51:47)
● 29 year old woman with intramural ileal tumor showing ALK/TPM3 fusion using FISH (Hum Pathol 2006;37:112)

Gross description
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● Mean 3-4 cm, submucosal sessile polypoid mass or multiple masses with broad base
● Tan-gray-yellow
● Overlying mucosa may be ulcerated

Micro description
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● Usually limited to submucosa
● Plump ovoid myofibroblastic spindle cells with inflammatory infiltrate including plasma cells and lymphocytes
● May be sparsely cellular with myxoid stroma
● May have rarefaction around muscular walled blood vessels
● May be infiltrative
● Cellular areas may have up to 2 mitotic figures/HPF
● Variable vascular component

Micro images
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Plump, ovoid myofibroblastic cells with pale eosinophilic cytoplasm in collagenous background with numerous lymphocytes and plasma cells

CD117- (endothelial cells are positive internal control)

Positive stains
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● Vimentin, muscle specific actin, smooth muscle actin, anaplastic lymphoma kinase (variable)

Negative stains
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● S100, desmin (Mod Pathol 2000;13:1134), CD117 (endothelial cells may be CD117+), CD34

Electron microscopy description
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● Myofibroblasts

Differential diagnosis
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● Fibromatosis: invades bowel secondarily

End of Small bowel (small intestine) > Benign tumors and tumor-like conditions > Inflammatory myofibroblastic tumor

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