Notch sign (primary CNS lymphoma)

Last revised by Dr Daniel J Bell on 03 May 2022

The notch sign refers to abnormally deep depression at the tumor margin in contrast-enhanced MRI in primary CNS lymphoma 1. It is not an uncommon sign in primary CNS lymphoma and can be seen in both immunocompetent and immunocompromised patients. It suggests an irregular growth pattern as well as pliable and infiltrative properties.

The notch sign is a specific feature for primary CNS lymphoma and can be helpful in differentiating CNS lymphoma in immunocompetent patients from glioblastoma multiforme (GBM) at the time of initial presentation according to one study 2.

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