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Liver and intrahepatic bile ducts - Tumor

Benign tumors

Inflammatory myofibroblastic tumor


Reviewers: Deepali Jain, M.D. (see Reviewers page)
Revised: 9 January 2013, last major update February 2012
Copyright: (c) 2004-2013, PathologyOutlines.com, Inc.

General
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● Uncommon lesion
● ALK1+: neoplastic lesion with intermediate biologic behavior
● ALK1-: considered reactive
● Also called inflammatory pseudotumor
● In extrapulmonary tumors, recurs locally in 25%; 8% metastasize
● Usually children and young adults; mean age 37 years but all ages, 75% male
● Associated with occlusive phlebitis and chronic cholangitis
● Rarely associated with sarcoma or follicular dendritic cell tumor
● Symptoms: fever, upper abdominal pain, jaundice

Treatment
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● Excision, occasionally regresses spontaneously

Gross description
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● Well-circumscribed, solitary (70%), 1-25 cm, variegated cut surface, may extend into vena cava or soft tissue, predominantly right lobe

Micro description
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● Plasma cells, lymphocytes, neutrophils, macrophages, mast cells and myofibroblast-like spindled cells in varying amounts, in whorled, fibrotic stroma
● Occasional myxoid areas, minimal vascular component; minimal pleomorphism, no/rare mitotic activity
● Rarely is highly cellular or has mitotic activity (often in children)
Aggressive morphologic features: p53+, ganglion-like cells, mitotic figures (Mod Pathol 1999;12:279); also epithelioid and round cell morphology, nuclear membrane staining of ALK (in contrast to diffuse cytoplasmic staining in benign (Am J Surg Pathol 2011;35:135)

Positive stains
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● Vimentin (>90%), smooth muscle actin (80%), muscle specific actin (80%), desmin (40%), CD68 (40%), pankeratin (30%), p53 (30%), ALK1 (50%)

Negative stains
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● S100, CD21, myoglobin

Differential diagnosis
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● Follicular dendritic cell tumors (CD21+, CD35+), Hodgkin lymphoma (stromal cells are CD15+, CD30+), IgG4 related pseudotumor (high ratio of IgG4+/IgG+ plasma cells, prominent lymphoid aggregates, absent ALK1 rearrangement, obstructive phlebitis, Mod Pathol 2011;24:606)
● Leiomyoma, organizing abscess, postoperative spindle cell nodule, sclerosing hemangioma, solitary fibrous tumor, spindle cell carcinoma or sarcoma

End of Liver and intrahepatic bile ducts - Tumor > Benign tumors > Inflammatory myofibroblastic tumor


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