Soft tissue
Fibroblastic / myofibroblastic
Inflammatory myofibroblastic tumor

Topic Completed: 1 May 2012

Minor changes: 25 February 2021

Copyright: 2002-2021,, Inc.

PubMed Search: Inflammatory myofibroblastic tumor of soft tissue

Komal Arora, M.D.
Page views in 2020: 23,576
Page views in 2021 to date: 11,506
Cite this page: Arora K. Inflammatory myofibroblastic tumor. website. Accessed May 6th, 2021.
Definition / general
  • Tumor of myofibroblasts with plasma cells, lymphocytes and eosinophils
  • Also called inflammatory fibrosarcoma, inflammatory pseudotumor, plasma cell granuloma
  • See also discussions in these chapters: Bladder, Breast, Colon tumor, Eye (orbit), Liver, Lung, Lymph node, Small bowel, Thyroid gland
  • Retroperitoneum (omentum) and mesentery in children and young adults (mean age 10 years)
  • Also lung, GI, GU, other sites
Clinical features
  • 1/3 have associated fever, growth failure, malaise, weight loss, anemia, thrombocytosis, polyclonal hyperglobulinemia and elevated sedimentation rate
  • Symptoms disappear after excision of mass (J Korean Med Sci 2002;17:699)
Prognostic factors
Case reports
Gross description
  • Circumscribed, not encapsulated
  • White tan mass with whorled fleshy or myxoid cut surface
  • May have focal hemorrhage, necrosis or calcification, mean 6 cm
Gross images

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Tumor at the mesentery of proximal jejunum

Mesentery of both jejunum and ileum

Well circumscribed, grayish white

Microscopic (histologic) description
  • Myofibroblastic and fibroblastic spindle cells with inflammatory infiltrate of lymphocytes, plasma cells, eosinophils, histiocytes
  • Background of abundant blood vessels
  • Mixture of three patterns:
    • Resembling nodular fasciitis with elongated myofibroblasts containing abundant eosinophilic cytoplasm and vesicular nuclei, loose myxoid stroma with neutrophils, lymphocytes and eosinophils, but few plasma cells;
    • Cellular with spindled myofibroblasts and fibroblasts in more compact stroma, arranged as islands surrounded by fibromyxoid stroma with prominent plasma cells and mitotic figures;
    • Densely hyalinized stroma with few spindle cells, few plasma cells or lymphocytes
  • May have ganglion-cell like myofibroblasts
  • All 3 patterns have no nuclear pleomorphism, no atypical mitotic figures
  • Malignant behavior: associated with highly atypical polygonal cells with oval nuclei, prominent nucleoli, Reed-Sternberg like cells, atypical mitotic figures
Microscopic (histologic) images

Case #400 - epithelioid inflammatory myofibroblastic sarcoma (EIMS):


Contributed by Mark R. Wick, M.D.

Various images


AFIP images

Typical appearance of spindled myofibroblastic cells and inflammatory infiltrate

Inflammation obscures the underlying myofibroblastic proliferation

Spindle cells are evident at high power

Tumor with more fibrous stroma

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Myofibroblasts and inflammatory cells

Retroperitoneal tumor

Positive stains
Electron microscopy description
  • Myofibroblastic cells and activated fibroblasts
Molecular / cytogenetics description
Molecular / cytogenetics images

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t(2;5) karyotype

ALK staining, FISH and karyotype

Differential diagnosis
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