Inflammatory Myofibroblastic Tumors Of The Genitourinary Tract--Single Entity Or Continuum?

Main Category: Urology / Nephrology
Also Included In: Cancer / Oncology
Article Date: 16 Nov 2008 - 0:00 PST

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UroToday.com - Can we meaningfully separate inflammatory pseudotumor (a term used since 1937 1 from inflammatory myofibroblastic tumor (IMT, a term introduced in 1990 for lung lesions 2 and from sarcoma?

The oldest large series of 38 such cases in the urinary bladder divided most of them into 17 pseudotumors and 13 sarcomas 3. The 17 patients in the pseudotumor group

1) had no tumor recurrence after resection,
2) histologically had no necrosis even if there was muscularis propria invasion,
3) had less nuclear atypia, and
4) p53 immunoreactivity was minimal to absent 3.

Recently, the term IMT has been used more than pseudotumor, but IMT may include a more aggressive but overlapping set of lesions. Perhaps whether ALK-1 rearrangements are detected in 8% of cases 4 or over half of cases 5, 6, depends on whether the lesions being studied are inflammatory pseudotumors 4 or IMT 5, 6. ALK-1 expression appears to correlate with local recurrence 5 and muscle invasion 6. IMT includes tumors with necrosis in up to 30% 6, and encompasses tumors with recurrence in up to 31% 6, so it is tempting to suggest that of the tumors we classified as sarcoma, at least the 7 low grade ones 3, most may have been considered by others as IMT, and conversely, that IMT is truly a low-grade sarcoma 7.

If the four criteria for inflammatory pseudotumor are applied as listed above, the calls to discourage use of this term 7 might be premature. Thus, although the terms inflammatory pseudotumor and IMT represent more reactive or more neoplastic points on a spectrum leading to malignancy, there remain at least some histologic factors that predict behavior, and there is some rationale for retaining the use of both terms.

It is promising that emerging molecular markers, such as ALK, may assist in accurate diagnosis, classification, and prognosis prediction.

References:

1. Lewis PM. Inflammatory Pseudotumor of the Orbit: Report of a Case. Trans Am Ophthalmol Soc 1937;35:328-35.
2. Pettinato G, Manivel JC, De Rosa N, Dehner LP. Inflammatory myofibroblastic tumor (plasma cell granuloma). Clinicopathologic study of 20 cases with immunohistochemical and ultrastructural observations. Am J Clin Pathol 1990;94:538-46.
3. Iczkowski KA, Shanks JH, Gadaleanu V, Cheng L, Jones EC, Neumann R, Nascimento AG, Bostwick DG. Inflammatory pseudotumor and sarcoma of urinary bladder: differential diagnosis and outcome in thirty-eight spindle cell neoplasms. Mod Pathol 2001;14:1043-51.
4. Chan JK, Cheuk W, Shimizu M. Anaplastic lymphoma kinase expression in inflammatory pseudotumors. Am J Surg Pathol;25:761-8.
5. Coffin CM, Hornick JL, Fletcher CD. Inflammatory myofibroblastic tumor: comparison of clinicopathologic, histologic, and immunohistochemical features including ALK expression in atypical and aggressive cases. Am J Surg Pathol. 2007;31:509-20.
6. Montgomery EA, Shuster DD, Burkart AL, Esteban JM, Sgrignoli A, Elwood L, Vaughn DJ, Griffin CA, Epstein JI. Inflammatory myofibroblastic tumors of the urinary tract: a clinicopathologic study of 46 cases, including a malignant example inflammatory fibrosarcoma and a subset associated with high-grade urothelial carcinoma. Am J Surg Pathol. 2006;30:1502-12.
7. Gleason BC, Hornick JL. Inflammatory myofibroblastic tumours: where are we now? J Clin Pathol 2008;61:428-37.

Written by Kenneth A. Iczkowski, MD, and Liang Cheng, MD, as part of Beyond the Abstract on Urotoday.com

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