A tumefactive demyelinating lesion (TDL) is a focus of demyelination that may mimic a brain tumor. It can rarely occur as a paraneoplastic syndrome.


Malignant diseases that have been associated with TDL:

(1) chronic monomyelogenous leukemia (CMML)

(2) seminoma

(3) malignant lymphoma


It is important to recognize the lesion:

(1) to avoid misdiagnosis of a brain metastasis

(2) to avoid an unnecessary invasive procedure


MRI imaging may show a number of findings which can help to suspect the diagnosis (see below).


Many patients respond to corticosteroid therapy.


Some paraneoplastic syndromes improve with treatment of the underlying tumor. This needs to be determined for TDL.


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