Isolated intracranial Rosai-Dorfman disease mimicking en plaque meningioma

We report a 47-year-old male patient under study for three recent episodes of seizures. Video EEG shows frequent slow and sharp abnormalities over the frontotemporal region, predominantly on the left side.

Unenhanced CT shows a hypodense lesion in the left temporal lobe (fig 1).

In the subsequent MRI there is a left temporal extra-axial lesion with meningeal thickening of laminar morphology. It is isointense on T1 WI (fig 2), hypointense on T2 WI sequence (fig 3), and with homogeneous enhancement the administration of gadolinium (fig 4). Vasogenic oedema in the white matter of the left temporal lobe is clearly depicted as high signal intensity on T2 Flair (fig 5).

In addition to these intracranial findings, we can also see contrast enhancement in the masticator space affecting the temporalis muscle compatible with tumour infiltration (fig 6).

Rosai-Dorfman disease is a rare entity characterized by non-Langerhans cell histiocytosis. It tends to be multifocal, most frequently involving the neck (lymphadenopathy), the intracranial compartment, or the spine. Multifocal involvement can be synchronous or metachronous. If Rosai-Dorfman disease is diagnosed only at one site, it may be required screening and follow-up for involvement in other parts of the body.

The most frequent presentation is a painless massive cervical lymphadenopathy (30-50% of cases). Extranodal presentation occurs in 40% of cases and in less than 5% of cases it appears isolated in the CNS with a radiological image similar to that of a meningioma [1, 3], as in the presented case. Rarely the disease can be purely intraparenchymal, and even intraventricular lesions have also been reported [4].

Due to their similarity, Rosai-Dorfman disease and en plaque meningioma can be indistinguishable on diagnostic imaging and pathological anatomy study became essential [1, 2].

In the study of an extra-axial lesion with thickening of the dura mater it is important to consider alternative diagnoses, especially if we see involvement of the adjacent soft tissues. The rare CNS localized Rosai-Dorfman should be remembered as differential diagnosis of meningiomas since they are similar radiologically and macroscopically. Intracranial Rosai-Dorfman disease is most frequently confused with meningioma, but it can also be confused with Langerhans cell histiocytosis, lymphoma, and other dural-based masses. [3].

Our patient underwent surgical treatment with resection of the lesion. In surgery the macroscopic appearance was that of a meningioma with little vascularization. The Anatomy department report was compatible with Rosai-Dorfman disease.

There is no specific therapy for Rosai-Dorfman disease. Resection is done the same way as in meningiomas, but depending on the case in some cases it can also be considered complementary chemotherapy or radiotherapy There are reports in which skull base lesions were successfully treated with corticosteroid agents.

The prognosis is generally described as benign. However, recurrence and fatal outcomes have been reported

In conclusion, intracranial Rosai-Dorfman is commonly confused radiologically with meningioma, and it is required histopathology and immunohistochemistry for the definitive diagnosis.