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Neuroradiology Case of the Week

Case 416

June 2009

Gurshawn Singh, MS2, and Rajiv Mangla, MD

Clinical Presentation: Patient is a 52-year-old female presenting with papilledema.

Imaging Findings: On MRI, there was significant pachymeningeal thickening with an enhancing dural based mass lesion in the right side of the posterior fossa seen along the tentorium and right transverse and sigmoid sinuses. There was also leptomeningeal enhancement seen in the adjacent cerebellar sulci. These lesions were iso to hypointense on T2 and T1-weighted images and showed intense homogeneous enhancement on post-contrast images. The right transverse and sigmoid sinuses were obliterated by the disease process. The CSF examination performed in the patient was suggestive of MALT lymphoma.

Diagnosis: Intracranial dural based MALT lymphoma

Discussion: Primary central nervous system lymphomas are very rare. This case is regarding a dural based low-grade lymphoma of mucosa-associated lymphoid tissue (MALT). These tumors are very rare, localized and involve the meninges. These are B-cell non-Hodgkin’s lymphomas which arise from meningoepithelial cells, which are present throughout the arachnoid membrane but present predominately in the arachnoid villi within dural venous sinuses. Where these meningoepithelial cells are aggregated and large in number are common regions for this tumor.
     Our case was seen in the region of right transverse sinus. Radiologically, they resemble meningiomas and subdural hematomas, and often times show the same clinical presentation. They appear as isolated, discrete extra-axial masses. Usually they are homogeneously enhancing and will have a wide dural base which may cause mass effect. In this case the tumor was localized to the dura causing obliteration of right transverse sinus. Since they can easily be diagnosed as meningiomas, it is important to have intracranial lymphomas as part of the differential diagnosis for extra-axial enhancing lesions.
     Few cases have been reported in the literature and most of them has been found in females. In a series of 14 cases, all were found to be in females only. MALT lymphomas are generally localized and do not spread much. They can be treated by combination of surgical excision and chemoradiotherapy, and usually have a good prognosis. Several cases have been reported to show complete regression on chemotherapy alone.

References:

1. Gupta P, Zhao QH, Rosovsky M, Madan A. B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma). Applied Radiology. 2005;32(5):50-54. http://www.medscape.com/viewarticle/504461
2. Pavlou G, Pal D, Bucur S, Chakrabarty A, van Hille PT. Intracranial non-Hodgkin's MALT lymphoma mimicking a large convexity meningioma. Acta Neurochir (Wien). 2006 Jul;148(7):791-3. [PubMed]