Background

Primary CNS lymphoma (PCNSL) accounts for 3% of all central nervous system (CNS) tumours with an incidence of around 2.7 cases per million per year. Prognosis is poor with an overall survival between 10.9 – 61.9 months. One of the key limitations in early treatment initiation is the delay in diagnosis caused by lack of recognition of a lesion as a suspected lymphoma, initiation of steroid treatment, lesion involution, and often a subsequent inconclusive biopsy. Inability to distinguish a probable lymphoma from a glioma on standard MRI imaging may lead to unnecessary surgical resection of this chemosensitive tumour.

Objective

We demonstrate that multiparametric MRI (MPMRI), which incorporates diffusion weighted imaging (DWI), perfusion weighted imaging (PWI) and magnetic resonance spectroscopy (MRS) is a valuable tool in addition to standard MRI modalities in resolving diagnostic uncertainty for PCNSL.

Methods

We present a series of 8 patients with histology-proven diffuse large B-cell lymphoma who underwent multiparametric imaging prior to biopsy at our centre (Queen Elizabeth Hospital Birmingham) due to equivocal appearances for lymphoma on standard MRI sequences, and describe the typical imaging features we note.

Results

Appearances on MPMRI shared similar features that increased the diagnostic likelihood of PCNSL - very low apparent diffusion coefficient (ADC) on DWI reflecting dense cellularity and low perfusion on PWI reflecting low angiogenesis. MRS demonstrated a high choline-creatine ratio reflecting high cellular membrane turnover, a high lipid peak due to macrophage infiltration, and very low NAA levels. This pattern of high choline and high lipid on MRS gives a ‘twin tower’ appearance, typical for PCNSL.

Conclusions

We propose multiparametric MRI as a tool to reduce the imaging-based diagnostic uncertainty for PCNSL. Concordance between two of three imaging multiparametric modalities could be used as a radiological predictor for PCNSL. We feel this could make histological confirmation redundant in selected cases – those with biopsy confirmed systemic high-grade lymphoma and a lesion typical for CNS involvement, patients with poor performance status suitable only for palliative chemotherapy and those with previous biopsy-confirmed PCNSL with a suspected relapse on imaging. Further, MPMRI may reduce the rate of steroid initiation for suspected lymphoma, provide a more accurate target for biopsy, and result in quicker tissue diagnosis and treatment initiation.