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inflammatory myofibroblastic tumor

Wednesday 3 February 2010

Definition: Inflammatory myofibroblastic tumor (IMT) is a distinctive lesion composed of myofibroblastic spindle cells accompanied by an inflammatory infiltrate of plasma cells, lymphocytes, and eosinophils. It occurs primarily in soft tissue and viscera of children and young adults (WHO, 2002).

Molecular subtypes

- ALK-associated inflammatory myofibroblastic tumor
- ALK-negative inflammatory myofibroblastic tumor

Images

- Inflammatory myofibroblastic tumor (IMT). IHC: ALK1. NB: spindle cell fascicles; prominent nucleoli; lymphoplasmacytosis.

IMT is composed of myofibroblastic spindle cells accompanied by an inflammatory infiltrate of plasma cells, lymphocytes, and eosinophils, usually occurs in the soft tissue and viscera of children and young adults, and may span the entire age range.

Inflammatory myofibroblastic tumor (IMT) is a neoplasm of intermediate biologic potential that frequently recurs and rarely metastasizes.

This distinctive neoplasm is composed of myofibroblastic mesenchymal spindle cells accompanied by an inflammatory infiltrate of plasma cells, lymphocytes, and eosinophils.

Although it occurs primarily in the lung, soft tissue, and viscera of children and young adults, in more recent years a broad age range has been documented.

Clinical synopsis

The clinical presentation is determined by the site of origin and the effects of the mass. A small proportion of patients have a syndrome of fever, weight loss, growth failure, malaise, anemia, thrombocytosis, polyclonal hyperglobulinemia, and elevated erythrocyte sedimentation rate.

The abdominopelvic region, lung, mediastinum, and retroperitoneum, are frequent sites, and uncommon sites include the central nervous system, upper respiratory track, solid organs, and soft tissue.

Molecular types

Approximately half of IMTs harbor a clonal cytogenetic aberration that activates the anaplastic lymphoma kinase (ALK)-receptor tyrosine kinase gene on the short arm of chromosome 2 at 2p23.

The discovery of ALK gene rearrangements in 50% to 75% of extrapulmonary IMTs supported the concept of IMT as a neoplasm.

The discovery in IMT of rearrangements of the ALK gene on chromosome 2p-23 has focused attention on the question of whether ALK-positive and ALK-negative IMTs have clinical and prognostic differences analogous to ALK-positive and ALK-negative anaplastic large cell lymphoma (ALCL).

In ALCL, expression of c-Myc, Bcl-2, and Mcl-1 is associated with ALK abnormalities, and expression of p27, CD56, and survivin seems to have prognostic significance. These markers have not been investigated in IMT.

In the past 2 decades IMT has been recognized as a lesion within the larger spectrum of lesions formerly known as inflammatory pseudotumors.

Atypical IMT

Past evidence has suggested that a combination of atypia, ganglion-like cells, p53 expression, and aneuploidy might characterize IMTs with more aggressive behavior, but in individual cases these are not reliable prognostic indicators.

Questions have arisen as to whether unusual or atypical histologic features such as necrosis, hypercellularity, and abundant ganglionlike cells have prognostic significance and whether a phenomenon previously described as malignant transformation portends a worse outcome.v

Molecular types

- ALK+ inflammatory myofibroblastic tumor
- ALK- inflammatory myofibroblastic tumor

  • HMGIC-associated inflammatory myofibroblastic tumor (10686944)

Treatment

At present, surgery is the principal treatment, although regression and response to antitumor necrosis factor-α binding antibody, corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), and chemotherapy have been reported in a few cases.

At present, IMT is regarded as a neoplasm of intermediate biologic potential because of the tendency for local recurrence, which is 25% for abdominopelvic lesions, and the rare incidence of metastasis.

References

- Inflammatory myofibroblastic tumor with HMGIC rearrangement. Kazmierczak B, Dal Cin P, Sciot R, Van den Berghe H, Bullerdiek J. Cancer Genet Cytogenet. 1999 Jul 15;112(2):156-60. PMID: 10686944

- Extrapulmonary inflammatory myofibroblastic tumor (inflammatory pseudotumor). A clinicopathologic and immunohistochemical study of 84 cases. Coffin CM, Watterson J, Priest JR, Dehner LP. Am J Surg Pathol. 1995 Aug;19(8):859-72. PMID: 7611533