Department of Pathology, University of Oklahoma Health Sciences Center

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Answer: A (Choroid plexus carcinoma)  Level of difficulty: 2 NeuroTest NeuroLearn NeuroHelp

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Discussion: 

• Pathology: The pathology of this case is that of a papillary neoplasm without associated brain tissue. Since it is removed from the lateral ventricle, the absence of accompanying brain parenchymal tissue suggest that the part of the tumor being shown here is probably an exophytic mass that protrudes into the ventricle. In general, the papillary structure is only partially maintained. Areas composed with sheets of cells and with focal necrosis (Þ). On higher magnification, the papillary structures has a basement membrane (Þ) and fibrovascular core There is significant nuclear pleomorphism and a mitotic figure (Þ) is in the photograph.In general, the focal loss of papillary pattern, and necrosis (n) are features suggestive of a papillary carcinoma and in this case, a choroid plexus carcinoma. 
• Clinical information: Choroid plexus tumors are common in children. Most often, they are choroid plexus papilloma and less frequently, choroid plexus carcinoma. The most common site is lateral ventricle and followed by the 4th ventricle. Tumors that are found in children under 2 years of age are mostly arising from the lateral ventricle. The third ventrice is an uncommon location. Although choroid plexus papilloma can be  seen in adults, choroid plexus carcinoma are almost unknown to adults. Choroid plexus papilloma in adults  tend to occur more frequently in the 4th ventricle. To make a diagnosis of choroid plexus carcinoma in adults, metastatic carcinoma must be ruled out. On the contrary, metastatic carcinoma is uncommon in childrens. 

Choroid plexus papilloma: It should not have loss of papillary structure, necrosis, and substantial pleomorphism. Mitotic figures should not be seen in choroid plexus papilloma.

Central neurocytoma: Although central neurocytoma usually arise within the lateral ventricle, they are uncommon in young children. In addition, their morphology is almost indistinguishable from oligodendrogliomas and do not possess architecture.

Hemangioblastoma: These tumors have clear cells and rich vascular supply. They do not form papillary structures.

Dysembryoplastic neuroepithelial tumor: These tumors are essentially benign glial-neuronal tumors and do not have papillary structures. Similar to choroid plexus tumors, they are usually seen in children.

Comment: KarMing-Fung@ouhsc.edu