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Case 418 - Discussion

Uploaded: 2010-08-08, Updated: 2010-09-08


Inflammatory myofibroblastic tumor / Inflammatory pseudotumor

  • Children and young adults, benign clinical course

  • Mostly viscera and soft tissue (mesentery and omentum)

  • Microscopic:

    • Spindle or stellate cells loosely arranged in a myxoid or hyaline stroma with inflammatory cells

    • Or, compact proliferation of spindle cells in a storiform or fascicular growth pattern

    • Tumor cells may have enlarged nuclei with prominent nucleoli, but lack of significant hyperchromasia or atypia

    • Some cells may resemble ganglion cells or RS cells

    • Prominent lymphoplasmacytic infiltrate in the background

  • IPX:

    • Positive: SMA, MSA, ALK1 (40%), keratin (1/3)

    • Negative: S100, CD117, CD34

  • Cytogenetics: clonal aberrations at 2p22-24, involving ALK gene

  • DDX:

    • Inflammatory MFH: bizarre pleomorphic cells

    • Inflammatory leiomyosarcoma: cigar-shaped nuclei in a more regular fascicular pattern

    • Inflammatory fibroid polyp: submucosal polyp of stomach and ileum, stellate cells, myxoid stroma, reactive vessels, inflammatory cells, particularly eosinophils

    • Idiopathic retroperitoneal fibrosis: older age, ill-defined mass, more prominent fibrosis and phlebitis

Reference: Enzinger and Weiss's Soft Tissue Tumors, 5th Edition. By Drs. Sharon Weiss and John Goldblum. 2007