Thursday 2 February 2012

Dense calcified 'Involuted sclerotic' / 'Psammomatous' Meningioma MRI

Non contrast CT
MRI T1, FLAIR, T2, Dwi, T2*GRE
Non contrast CT shows a left frontal ovoid well demarcated mass at the floor of anterior cranial fossa, isodense to bone. On MRI, lesion show uniform low signals on all pulse sequences including T2*GRE implies to dense calcification. Marked perilesional vasogenic odema in adjacent left frontal lobe white matter on FLAIR.
MR Spectroscopy, going to be non contributory in this case as lesion is densely calcified.

Histopathology report: 

Description of finding: The resected specimen consist of an irregular, firm, bosselated, tan-white nodule with an attached dura mater on one side. The specimen fixed in buffered 10% formaldehyde and decalcified. Paraffin-embedded sections stained with H n E stain. The tissue consisted primarily of densely packed hyalinized collagen bundles. Major portion virtually acellular, occasional small nests of uniform meningothelial cells. Few areas of whorllike arranged collagen fibers.

- 'Psammomatous' variety of Meningioma.

Dense calcified Meningioma
Syn: 'Involuted sclerotic' Meningioma, 'Psammomatous' Meningioma.

Involuted sclerotic meningioma is a distinct subtype of benign meningioma that lack the classic appearance and manifestation of typical meningothelial meningiomas.
A classic meningioma on CT is a relatively hyper attenuating, extra axial mass broad based to Dura with a smooth or lobulated outline that enhances homogeneously on post contrast study. Most common histopathological variety of typical meningioma is fibrous meningioma shows parallel and interlacing bundles of spindle-like cells embedded in a matrix of collagen and reticulin on Histopathology.
Whereas a sclerotic meningiomas demonstrate whorl formation around sclerotic vessels, with tumor cells demonstrating glial fibrillary acidic protein expression. Due to dense calcification these masses are iso dense to bony calvarium on CT, contrast enhanced studies are non contributory as enhancement if any is difficult to interpret in the back ground of dense calcification. On MRI, lesion is low signal intensity on all pulse sequences, poor or partial enhancement on post contrast. Dural tailing on post contrast and focal hyperostosis of adjacent bony calvarium of a typical meningioma are absent.

Differential diagnosis for an extra axial calcified mass at the cerebral convexity without dural tailing or bone reaction should include osteoma.

Similar case: Psamomatous-meningioma

Reference : Best Cases from the AFIP Involuted Sclerotic Meningioma, Radiographics.

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