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Neuroradiology Case of the Week

Case 360

November 2008

Daniel Ginat, MD, MS and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a one-year-old female with hydrocephalus.

Imaging Findings:
Non-contrast Head CT: Third ventricular midline mass, measuring approximately 32 x 38 mm, with cauliflower morphology. The mass is heterogeneous and contains multiple coarse foci of calcification. The mass produces obstructive hydrocephalus as evidenced by dilatation of lateral ventricles.
Gd-enhanced MRI: Heterogeneously enhancing, lobulated intraventricular mass arising from the third ventricle with extension into the right and left lateral ventricles with hydrocephalus.
Pathology: Delicate fibrovascular cores are covered in some areas by a single layer of cuboidal to columnar epithelial cells with monomorphic nuclei, but in other areas these cores are covered by multilayered, more pleomorphic cells. A rare area is assuming a solid pattern. There are several areas of focal necrosis. The mitotic index is 4 per 10 high power fields.

Diagnosis: Atypical Choroid Plexus Papilloma (WHO II)

Discussion: Choroid plexus papillomas comprise approximately 3% of childhood intracranial tumors with onset usually before the age of 10, although adult may be affected as well [1-2]. Choroid plexus tumors most commonly arise in the lateral ventricles (50%) and fourth ventricle (40%) [2]. In 5% of patients, choroids plexus papillomas may be located within the third ventricle and another 5% are multifocal [2]. Extraventricular sites of origin are very rare. Choroid plexus tumors are associated with SV 40 exposure, Li-Fraumeni syndrome, and Aicardi syndrome [1-2].
     Typical imaging characteristics on CT include isodense to hyperdense “mulberry” or “cauliflower-like” appearance, which describes prominent peripheral lobulations [1-2]. Calcifications in 20 to 25% of cases and cyst formation and hemorrhage can occur [1-2]. On MRI, there is decreased signal on T1 and heterogeneous signal on T2 [1]. Flow voids may also be seen [2]. These tumors can attain large proportions and cause hydrocephalus and papilledema. Necrosis and significant heterogeneity, however, is more typically seen in choroid plexus carcinomas. Other differential considerations include hemangiomas, ependymomas, lymphoma, meningioma, and metastatic disease.
     Malignant transformation of choroids plexus papillomas to carcinoma occurs in a small subset of patients [3]. In addition, choroid plexus papillomas have the potential to seed to the spine; therefore, follow-up with contrast-enhanced MRI of the spine is suggested, particularly with atypical varieties [2,4]. Recurrence after gross total resection occurs in an estimated 6% of patients with choroid plexus papillomas and 29% of patients with atypical choroids plexus papillomas [3]. Atypical choroids plexus papillomas are classified as WHO II and demonstrate mitotic activity, increased cellularity, nuclear pleomorphism, and necrosis [4].

References:

1. Grossman RI, Yousem DM. Neuroradiology: The Requisites, vol. 2, Philadelphia: Mosby/Elsevier, 2003: 111-114.
2. Koeller KK, Sandberg GD; Armed Forces Institute of Pathology. From the archives of the AFIP. Cerebral intraventricular neoplasms: radiologic-pathologic correlation. Radiographics. 2002 Nov-Dec;22(6):1473-505. [PubMed]
3. Jeibmann A, Wrede B, Peters O, Wolff JE, Paulus W, Hasselblatt M. Malignant progression in choroid plexus papillomas. J Neurosurg. 2007 Sep;107(3 Suppl):199-202. [PubMed]
4. Jeibmann A, Hasselblatt M, Gerss J, et al. Prognostic implications of atypical histologic features in choroid plexus papilloma. J Neuropathol Exp Neurol. 2006 Nov;65(11):1069-73. [PubMed]