Unusual variants of primary central nervous system lymphoma.

Rare variants of primary central nervous system lymphoma (PCNSL) include unusual sites of presentation (eg, neurolymphomatosis and primary leptomeningeal lymphoma) and uncommon pathologic entities. Neurolymphomatosis involves peripheral nerves and nerve roots in addition to systemic and central nervous system (CNS) sites. Diagnosis requires a high index of suspicion, and treatment incorporates the principles of therapy for systemic and CNS lymphoma. Primary leptomeningeal lymphoma can present with symptoms of raised intracranial pressure or cranial or spinal polyradiculopathies. Diagnosis can be made by examining cerebrospinal fluid and incorporating immunophenotyping and molecular pathology techniques. Treatment options include irradiation and intrathecal or systemic chemotherapy. The features of PCNSL of T-cell origin and indolent B-cell PCNSL also are discussed.