Mesenchymal tumors

Inflammatory myofibroblastic tumor

Last author update: 3 March 2021
Last staff update: 26 April 2023

Copyright: 2003-2023,, Inc.

PubMed Search: Inflammatory myofibroblastic tumor [title] colon

Raul S. Gonzalez, M.D.
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Cite this page: Gonzalez RS. Inflammatory myofibroblastic tumor. website. Accessed June 2nd, 2023.
Definition / general
  • Low grade mesenchymal neoplasm that can arise in the colonic wall or mesentery, usually of children
  • See also topic in Soft tissue chapter
Essential features
  • Mesenchymal neoplasm, often pediatric, with spindled cells admixed with inflammation
  • t(2;5) (TPM3-ALK) translocation
  • Rare aggressive variant called epithelioid inflammatory fibroblastic sarcoma
  • Older terms include called inflammatory pseudotumor, inflammatory fibrosarcoma and plasma cell granuloma
  • Epithelioid inflammatory fibroblastic sarcoma refers to a rare, aggressive variant with unique morphologic and molecular features (Am J Surg Pathol 2011;35:135)
  • Can arise in the colonic wall or the mesentery
  • Most common site in gastrointestinal tract is stomach
Clinical features
  • Patients usually in the pediatric age range (Am J Surg Pathol 2007;31:509)
  • Symptoms include anemia, abdominal pain, fever, weight loss and high sedimentation rate (J Pediatr Surg 2001;36:169)
  • May recur but metastases rare; these outcomes may be more common in epithelioid inflammatory fibroblastic sarcoma
Radiology images

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Polypoid lesion, on imaging

Case reports
Clinical images

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Endoscopic view of polypoid lesion

Gross description
  • Circumscribed, often polypoid
Gross images

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2 cm polypoid lesion with central depression

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3.9 cm fungating yellow mass

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2 year old boy with colonic mass causing anemia

Microscopic (histologic) description
  • Bland spindle cells with abundant amphophilic cytoplasm and variably prominent nucleoli
  • Lymphoplasmacytic infiltrate with polyclonal plasma cells
  • Background may show myxoid change or laminated / whorled fibrosis
  • Epithelioid inflammatory myofibroblastic sarcoma: similar, except cells are more epithelioid, with large nucleoli
Microscopic (histologic) images

Contributed by Raul S. Gonzalez, M.D.
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Not necessarily colon

Contributed by Michael Feely, D.O.
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Epithelioid inflammatory myofibroblastic sarcoma

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Various images (H&E and IHC)

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Spindle cells
in hyaline
stroma, with

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for vimentin
and smooth
muscle actin

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Inflammatory cells and spindle cells

Positive stains
Negative stains
Molecular / cytogenetics description
  • Abnormalities of 2p23, usually t(2;5) (TPM3-ALK) translocation, in approximately half of cases; more common in children (Mod Pathol 2001;14:569)
  • Epithelioid inflammatory myofibroblastic sarcoma: t(2;2) RANBP2-ALK translocation
Sample pathology report
  • Ascending colon, resection:
    • Inflammatory myofibroblastic tumor (3.1 cm) (see comment)
    • Margins of resection unremarkable.
    • Two benign lymph nodes.
    • Comment: An immunostain for ALK1 is positive in the tumor.
Differential diagnosis
Board review style question #1

A young male patient presents with abdominal pain. Imaging reveals a large mesenteric mass, which is resected. An image of the tumor’s histology is seen above. Immunohistochemistry shows ALK1 staining of the nuclear membranes. What molecular abnormality is present in this tumor?

  1. ALK1 deletion
  2. ALK1 inversion
  3. t(2;2) RANBP2-ALK translocation
  4. t(2;5) TPM3-ALK translocation
Board review style answer #1
C. t(2;2) RANBP2-ALK translocation. This is an epithelioid inflammatory myofibroblastic sarcoma.

Comment Here

Reference: Inflammatory myofibroblastic tumor
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