|
|
Magnetic resonance imaging
MicroscopyT1- and T2-weighted MR images through the skull show a lesion in the parietal cortex that is hypointense on T1 and heterogeneously bright on T2. Though large, the lesion is not causing significant mass effect; the adjacent sulci are not effaced and the ventricles are symmetric. The appearance is non-aggressive; there is no edema visible on the T2-weighted image. The post-contrast image shows a mural nodule (non-enhancing rim) with an adjacent cystic area.
No gross images were presented for this particular case; the sample image shows the characteristic gross appearance of a cystic mass. Low-power microscopy shows an eosinophilic appearance. At higher power, numerous neoplastic cells are visible; the morphology is consistent with ganglion cells. Immunohistochemical analysis confirmed the diagnosis.
Radiology Discussion:
The differential diagnosis for a cystic mass (with enhancing nodule) within the brain includes pleomorphic xanthoastrocytoma (PXA), pilocytic astrocytoma, hemangioblastoma, and ganglioglioma/gangliocytoma. This discussion will provide an overview of each.
Pleomorphic xanthoastrocytoma typically occurs in children and young adults; two-thirds of all cases occur in patients under the age of 18 years. There is no gender association. PXA generally arises in the cerebral hemispheres; it is usually superficial and in temporal lobes. The most common presenting symptom is seizure. PXA represents less than 1% of all astrocytic neoplasms. The prognosis is fairly good, with a five-year survival rate of 80%. On imaging, 1/3 -1/2 of PXA lesions have a cystic component. Calcification and hemorrhage are rare. On CT, the mass may appear either hypodense or cystic with an intensely enhancing, isodense solid nodule. On MR, this cortical mass will display low/mixed T1 signal and high/mixed T2 signal. The solid components will enhance avidly; adjacent meninges may also enhance. There is generally little mass effect.
Pilocytic astrocytoma is a pediatric diagnosis. In fact, it is the most common infratentorial neoplasm in children. The majority of these lesions (60%) occur in the posterior fossa; other sites include the optic pathways and the hypothalamus. This benign entity is associated with a five-year survival rate of 90%. Approximate one-half of pilocytic astrocytomas are cystic masses with a mural nodule, while the remainder are solid. The solid lesions tend to be more aggressive. On CT, the lesion is a well-defined cystic cerebellar mass; the solid components are typically iso- to hypodense. On MR images, the lesion generally has low T1 and high T2 signals as well as an intensely enhancing mural nodule. Calcification and hemorrhage are rare.
Hemangioblastoma occurs in young and middle-aged adults and is more common among men than women. It is the most common primary intraaxial tumor of the posterior fossa in adults; other sites that may be affected include the spinal cord, medulla, and cerebrum. Common presenting symptoms include headache, ataxia, nausea/vomiting, and vertigo. The lesion is sometimes (25% of cases) associated with von Hippel-Lindau disease. The five-year survival rate is 85%. The appearance on CT is variable. In many cases (40%), this lesion is entirely solid and enhances avidly. In other cases, it is a cystic mass in the cerebellum with a slightly hyperdense, intensely enhancing nodule. On MR, the lesion displays low T1 signal compared to gray matter. The T2 signal is typically high. Serpentine signal voids represent feeding vessels. Angiography shows a vascular nodule within an avascular mass.
Ganglioglioma contains both glial and neuronal components and can undergo malignant degeneration (rarely). Gangliocytoma is composed entirely of neuronal components and is completely benign. Both occur primarily in children and young adults and affect the temporal lobes and cerebellum. One-third to one-half of gangliogliomas are cystic; one-third have calcifications. The lesion is hypo- to isodense on CT. If the lesion is cystic, MR evaluation will show low T1 and high T2 signals with variable, often peripheral, enhancement. If a mural nodule is present, it will enhance with contrast. Gangliocytoma, on the other hand, is hyperdense on CT and displays isointense T1 and T2 signals on MR (although it is hyperintense on FLAIR).
Brant W, Helms C. Fundamentals of Diagnostic Radiology. Philadelphia, PA: Lippincott Williams & Wilkins;1999.
Dear Visitors: Nothing on this World Wide Web site should be considered medical advice. Only your own doctor can help you make decisions about your medical care. It is not the policy of the Brigham and Women's Hospital Department of Radiology to provide consultation on the World Wide Web or via e-mail. If you have a specific medical question or are seeking medical care, please call the Brigham and Women's Hospital toll-free physician referral line at 1-800-294-9999.
Is this a mirrored page?
The official homepage of the BrighamRAD Teaching Case Database is http://brighamrad.harvard.edu/education/online/tcd/tcd.html
Contact the BrighamRAD Design Team for additional information about this website.