Choroid plexus papilloma of the cerebellopontine angle.

Choroid plexus papillomas are rare tumors, representing less than 1% of all intracranial neoplasms in our review of the English literature. Derived from the neuroepithelial cells of the choroid plexus, these tumors recapitulate the structure of the normal choroid plexus, often demonstrating a well-developed papillary architecture. This tumor most commonly affects children and typically arises in the lateral ventricles.

Malignant transformation of nasopharyngeal lymphoid hyperplasia.

Lymphadenopathy and nasal obstruction are very common in the HIV-positive patient and may or may not reveal a nasopharyngeal tumor. Biopsy is warranted if there is evidence suggestive of lymphoma or other neoplastic disease. This would include progressive rapid enlargement observed on examination or CT scan, an asymmetric growth pattern, and evidence of invasion of normal anatomic boundaries.