Intraparenchymal Primary CNS Marginal Zone Lymphoma: A Rare Disease or Rather a Highly Misdiagnosed Condition? A Case Report and a Literature Review

1. Abstract 1.1. Context: Marginal zone lymphoma, also known as mucosa associated lymphoid tissue (MALT) lymphoma, is a low-grade neoplasm generally with good prognosis and treatable with radiotherapy – rarely has its initial presentation in the CNS. When it does, a dural presentation is more common. However, it represents an even more infrequent condition when it appears as a primary intraparenchymal lesion and tends to be misdiagnosed: a potential problem because, almost always, a less invasive approach is adequate as treatment. 1.2. Goal: This article brings forward a rare case of intraparenchymal primary CNS marginal zone lymphoma (PCNS MZL), aiming to add information to the literature about this atypical case and its diagnostic and therapeutic approach. 1.3. Method: We made a case report and a literature review. 1.4. Results: This article describes a rare condition that was reported only in few other studies, as well as the process of diagnosis and treatment, which led to a partial remission of the lesion and to a reduction of clinical features. 1.5. Conclusion: Intraparenchymal PCNS MZL is a rare and, possibly, underdiagnosed condition and should be remembered when facing an intraparenchymal brain mass. Further studies are required to develop protocols that ensure a more precise diagnostic reasoning considering this condition. 2. Introduction Primary CNS lymphomas are rare. The vast majority of cases in immunocompetent patients comprise the high grade Diffuse large B-cell lymphomas (DLBCLs), that typically are intraparenchymal. Accounting for the minority of lymphoma cases with initial presentation in the CNS, we have low grade lymphomas, that typically do not involve cerebral tissue and have predominant dural location, resembling meningiomas. [1, 2] [5]. This article is about an extremely rare presentation of an intraparenchymal primary CNS lymphoma: Primary CNS Marginal Zone Lymphoma (PCNS MZL) with no dural presentation – an indolent, low-grade lymphoma. [1-3] [5] MZL is also known as Mucosa Associated Lymphoid Tissue (MALT) lymphoma [11]. We provide a case report and a literature review of intraparenchymal PCNS MZL with a search that included all combinations of the following terms in the baselines PUBMED, MEDLINE and LILACS: ((marginal zone lymphoma) OR (mucosa-associated lymphoid tissue lymphoma) OR (MALT-type lymphoma) OR (MALT lymphoma) OR (MALToma) OR (low grade B cell lymphoma)) AND ((CNS) OR (Central Nervous System)) AND ((primary) OR (initial presentation)) AND (case report). After the primary selection, we excluded articles that didn ́t fit the criteria “intraparenchymal marginal zone lymphoma with initial presentation in the CNS” by analyzing titles and abstracts – that resulted in just five case reports. 3. Case Report The patient is a 40-year-old woman HIV negative with a history of seizure and headache. At admission, she presented with right frontoparietal headache and focal seizure with motor activity in the left upper limb, without impairment of awareness. At physical examination, no abnormalities but the focal seizure were found. Enhanced MRI disclosed a right frontoparietal lesion with the following features: infiltrative and expansive cortical-subcortical formation with high signal intensity on T2 and FLAIR (Figures 1A and 2-a). Enhanced MRI also showed high signal intensity on