Non-enhancing primary CNS lymphoma

Abstract

Primary central system lymphomas (PCNSL) are highly proliferative tumors that require aggressive treatment, e.g. using high-dose methotrexate-based chemotherapy. Early histological diagnosis is crucial for proper management of PCNSL. Histological diagnosis is obtained through stereotactic biopsy which is usually performed upon demonstration of the typical hallmarks of PCNSL on MRI. This includes large, preferentially periventricular, homogenously contrast-enhancing lesions [1]. Although the MRI presentation of PCNSL is relatively uniform regarding the appearance as homogenously contrast-enhancing lesion(s), the MRI presentation of PCNSL may very rarely be atypical [2, 3] and may lead to significant delay in diagnosis and therapy initiation in such patients. We here present a patient with the rare case of a PCNSL without contrastenhancement. An 81-year-old patient presented with a 5-week history of rapidly progressive dementia. On examination, he was disoriented and showed psychomotor slowing and gait difficulty. The Mini Mental state examination (MMSE) revealed 16/30 points. He was HIV negative and all serological and biochemical tests were normal. The CSF examination showed just a slight increase in protein content (556 mg/l), no pleocytosis and no atypical cells. The MRI of the brain taken without prior steroid treatment revealed diffuse white matter changes involving both hemispheres. No pathological contrast-enhancement could be detected (Fig. 1). A diagnosis of gliomatosis cerebri was initially suspected. A biopsy was taken from the right frontal lobe. Histological examination revealed a diffuse large cell lymphoma (non-Hodgkin’s lymphoma of germinal B cell origin; Fig. 2). The present case highlights the fact that, in very rare cases, PCNSL may present as a non-enhancing lesion. Non-enhancing presentation was found in 1% of patients in a large series of immunocompetent patients [1] and is just one form of atypical MRI presentation of PCNSL. Another atypical form is the presentation with a central nonenhancing necrosis; this is found in 6–17% of immunocompetent PCNSL patients [1]. PCNSL without contrast uptake are usually caused by angiotropic large cell lymphoma or intravascular lymphomatosis [4]. In contrast, the present case did not show a particular angiotropic pattern but had the typical pattern of a diffuse large cell lymphoma with some perivascular accentuation (Fig. 2c). Unusual non-enhancing presentation may lead to substantial prolongation of definitive diagnosis and start of therapy. This underlines that PCNSL without contrast-enhancement has to be kept in the differential diagnosis of diffuse white matter disorders. Also, it further supports the importance of histologic verification before the onset of therapy. Since histological diagnosis of PCNSL may be greatly hampered by the use of lympholytic steroids prior to biopsy, it M. L. Lachenmayer and E. Blasius contributed equally.