Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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August 19, 2021
Inflammatory Myofibroblastic Tumor
- Background:
- Also known as inflammatory pseudotumor
- Tumor consisting of myofibroblastic spindle cells with an incidence of 0.04–0.7%
- It can have a bacterial etiology: Mycobacterium, Nocardia, or Epstein-Barr virus.
- They are usually seen in children or young adults less than 16 years of age.
- Commonly seen in the orbit (10% of orbital masses), lung (50% of benign tumors in children, 0.7% of lung tumors), and abdomen (71% of cases in liver); rarely in the spine, with only 12 cases reported in the literature thus far
- Histology reveals myofibroblastic and fibroblastic spindle cells with an inflammatory infiltrate of lymphocytes, plasma cells, and eosinophils.
- Chronic inflammation and fibrosis leading to collagen deposition show up as areas of hypointensity on T2WI.
- Vimentin and sometimes ALK1 stain positive in up to 40% of cases
- Clinical Presentation:
- Can present with fever, weight loss, night sweats, or pain with features of local mass effect causing myelopathy if the lesion is within the spine
- Key Diagnostic Features:
- Mixed areas of signal hyperintensity and hypointensity on T1WI, T2WI with cord compression, as seen in this case
- T1WI C+ (Gd): Vivid enhancement
- Calcification can be seen in 15% of cases.
- Differential Diagnoses:
- Neoplastic: Lymphoma (usually more hyperintense on T2WI), hemorrhagic metastasis (a primary lesion would be expected on PET-CT), solitary fibrous tumor (usually low to intermediate on T1WI and T2WI), hemangiopericytoma (usually intermediate signal on T2WI)
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Pseudoneoplasm: Calcified pseudoneoplasm of the neuraxis (usually minimally enhancing)
- Inflammatory: IgG4 disease (can be hyperintense or hypointense on T2WI), chronic granulomatous disease including granulomatosis with polyangiitis (formerly Wegener granulomatosis, usually necrotic with rim enhancement)
- Infection with fibrosis/granulomatosis: Aspergillus, Cryptococcus, Histoplasma, Epstein-Barr virus, cytomegalovirus, measles, tuberculosis (excluded by patient’s history)
- Unlikely in this demographic: Fibrotic meningioma, epidural fibrosis (no history of disc herniation or surgery)
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Treatment:
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Cure is achievable with complete surgical resection. Recurrence is seen in up to 40% of cases. 11% of cases metastasize.
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Alternative treatments are steroid therapy with radiotherapy or chemotherapy (methotrexate, vinorelbine/vinblastine).
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