Cryptococcoma Differential Diagnosis
see also Cryptococcoma Diagnosis.
Cryptococcal meningitis is the most common type of cryptococcosis involvement. Mass-effect lesions are uncommon: they are described as cryptococcomas and their prevalence is even lower among immunocompetent patients 1).
Primary and secondary brain tumors are usually the first hypotheses in these cases. Thorough preoperative investigation through cerebrospinal fluid sampling and detailed magnetic resonance imaging may lead to consideration of this diagnosis before the histopathologic analysis has been conducted 4)
The aim of a study was to detect and localize fungal brain lesions caused by Cryptococcus species based on Chemical Exchange Saturation Transfer (CEST) MR imaging of endogenous trehalose, and hereby to distinguish cryptococcomas from gliomas. In phantoms, trehalose and cryptococcal cells generated a concentration-dependent CEST contrast in the 0.2 – 2 ppm chemical shift range, similar to glucose, but approximately twice as strong. In vivo single voxel MRS of a murine cryptococcoma model confirmed the presence of trehalose in cryptococcomas, but mainly for lesions that were large enough compared to the size of the MRS voxel. With CEST MRI, combining the more specific CEST signal at 0.7 ppm with the higher signal-to-noise ratio signal at 4 ppm in the CryptoCEST contrast enabled localization and distinction of cryptococcomas from the normal brain and from gliomas, even for lesions smaller than 1 mm3. Thanks to the high endogenous concentration of the fungal biomarker trehalose in cryptococcal cells, the CryptoCEST contrast allowed identification of cryptococcomas with high spatial resolution and differentiation from gliomas in mice. Furthermore, the CryptoCEST contrast was tested to follow up antifungal treatment of cryptococcomas. Translation of this non-invasive method to the clinic holds potential for improving the differential diagnosis and follow-up of cryptococcal infections in the brain 5).
The aim of a study is to highlight the importance of cryptococcosis as one of the most common fungal infections of the central nervous system, stressing the consideration of a cryptococcoma within the list of differential diagnosis of intraventricular masses in immunocompetent hosts 6).
A 54-year-old man presented with two episodes of dysarthria and left facial droop. Both episodes resolved by the time of examination. MRI of the brain revealed a right frontotemporal, heterogeneously enhancing mass with surrounding vasogenic oedema, suggestive of a high-grade primary brain neoplasm. The patient was administered preoperative 5-aminolevulinic acid hydrochloride (Gliolan), and fluorescence-guided resection of the lesion was undertaken. Cryptococcus gattii infection was diagnosed from the specimen and the patient was given appropriate antifungal treatment. This is the first reported case of Gliolan-mediated fluorescence in a fungal abscess and highlights one of the potential pitfalls in fluorescence-guided surgery 7).
Cryptococcal CNS infections in immunocompetent hosts can mimic the intraventricular form of racemose neurocysticercosis. Distinguishing between the two is essential because the medical management of the 2 conditions is distinct from each other 8).
Yeh CH, Lin SF, Chiu MC, Kuo CL, Huang HT, Shoung HM. Cerebral Cryptococcoma in an HIV-Negative Patient: Experience Learned From a Case. J Neuropsychiatry Clin Neurosci. 2014 Fall;26(4):E34-5. doi: 10.1176/appi.neuropsych.13070161. PMID: 26037882.