Sunday 31 May 2015

Posterior Fossa Mass MRI

Clinical Details  : About four to five months history of headaches over the vertex and the occipito-nuchal region, constant, not associated with any vomiting or blurring of vision. She has also been complaining of some blurring of vision. Examination shows papilloedema in the right eye. No other signs. 
Previous CT shows mild ventriculomegaly and an enhancing posterior fossa lesion behind right cerebellum with some degree of compression over 4th ventricle.
Advised MRI for better evaluation.


Multi planner multi echo MRI study of brain has been performed. Sequences planned are FSE T1W, FSE T2W, FLAIR, and DW images. PC T1. 
Single voxel MR Spectroscopy. 

An extra axial dural based ~ 60x30mm well-demarcated mass at the floor of posterior cranial fossa extending beyond foramen magnum in spinal canal, compressing cerebellar hemispheres , medulla and vertebrals at foramen magnum. Obstructive hydrocephalus due to fourth ventricle compression, peri ventricular ooze of Csf. 
No marked perilesional odema. Lesion is homogenously iso intense on cortical gray matter on T1 and iso intense on T2 images with homogeneous enhancement on post contrast T1.
On MRS, No NAA peak, significantly reduced Creatinine. High choline and choline -creatinine ratio. 

Impression: Imaging wise diagnosis given was Meningioma.


Posterior fossa craniotomy done with complete excision of lesion.

Histopathology report

A high grade extra medullary myeloid cell tumor without any lineage differentiation.
The tumor cells express LCA, Mic 2 Weak , CD 3, TdT few cells and CD10 and are CD 33, 7, 68, 61 and Glycophorin C.
The Mib 1 labeling index is approximately 50%

Impression : High grade extra medullary myeloid cell tumor without any lineage differentiation - LYMPHOMA.

" This is second time that Lymphoma has surprised me". 

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