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Fibrosing inflammatory pseudotumors involving the skull base: MR and CT manifestations with histopathologic
1Department of Diagnostic Radiology, Seoul (Korea) National University College of Medicine.
Purpose:
To describe the MR and CT features of fibrosing inflammatory pseudotumors of the skull base region, and to document the MR signal intensity of the lesions with histopathologic comparison.
Methods:
We reviewed the MR and CT studies of five patients with pathologically proved fibrosing inflammatory pseudotumor involving the skull base. Unenhanced spin-echo T1- and T2-weighted and contrast-enhanced T1-weighted MR images were obtained at 0.5 T in three patients and at 1.5 T in two patients. MR findings were correlated with histopathologic findings in all five cases, and the enhancement pattern was compared with CT findings in three cases.
Results:
In three cases, the cavernous sinus was involved unilaterally, with adjacent extracranial infiltrative masses. In one case, both orbits, the cavernous sinuses, and the tentorium were involved with diffuse infiltrative lesions. One patient had an infiltrative nasopharyngeal mass; and in all five patients, MR images showed localized involvement of the skull base, with bone marrow replaced by tumor. The soft-tissue lesions were hypointense on T2-weighted images in all five cases and showed homogeneous contrast enhancement. Histopathologic studies revealed scanty inflammatory cell infiltration with densely fibrotic background in all cases. The hypointensity of the lesions on T2-weighted images seemed to be related to the degree of fibrosis.
Conclusion:
Fibrosing inflammatory pseudotumor shows characteristic MR findings of infiltrative lesion with bone destruction and hypointensity on T2-weighted images. The lack of mobile protons due to the fibrotic background and/or high cellularity of the lesions may be the reason for their hypointensity and weaker enhancement on MR images.
Insights
Fibrosing inflammatory pseudotumors of the skull base present as infiltrative lesions with bone destruction. These tumors show hypointensity on T2-weighted MRI, likely due to fibrosis.
Area of Science:
- Radiology
- Pathology
- Oncology
Background:
- Fibrosing inflammatory pseudotumors are rare neoplastic entities.
- Skull base involvement presents diagnostic challenges.
Purpose of the Study:
- Describe MR and CT features of skull base fibrosing inflammatory pseudotumors.
- Correlate MR signal intensity with histopathology.
Main Methods:
- Retrospective review of 5 patients with pathologically proven lesions.
- Analysis of unenhanced and contrast-enhanced T1/T2-weighted MRI and CT scans.
- Correlation of imaging findings with histopathology.
Main Results:
- All 5 patients showed infiltrative lesions with skull base bone marrow replacement.
- Lesions were hypointense on T2-weighted MRI and showed homogeneous enhancement.
- Histopathology revealed dense fibrosis with scanty inflammatory cells.
Conclusions:
- Fibrosing pseudotumors exhibit characteristic MRI findings: infiltrative nature, bone destruction, and T2 hypointensity.
- Fibrosis and/or high cellularity likely cause T2 hypointensity and weaker enhancement.