Primary malignant lymphoma is an uncommon disease of the central nervous system (CNS). Immunocompromised patients are at high risk of development of malignant lymphoma. We describe a case of primary CNS lymphoma presenting as a solitary cerebellopontine angle lesion. The patient had undergone extirpation of rectal cancer four years previously. Malignant lymphoma presenting as a cerebellopontine angle mass is extremely rare, with only 10 such cases (seven were primary, and the others secondary) previously reported.