Primary central nervous system lymphoma (PCNSL) is an extranodal non-Hodgkin lymphoma arising from and confined to the neuraxis. It represents about 3-4% of all primitive brain neoplasms and is mainly located in deep supratentorial regions. A ventricular involvement is quite frequent, but in the vast majority of cases it is secondary to an extension from a subependymal location. Amongst the primary ventricular forms occasionally reported, a choroid plexus origin is extremely rare; to date, only three cases have been described in the English literature. We report the case of a 71-year-old left-handed woman admitted to our department after a progressive 2-week history of confusion, motor speech disturbances and left hemiparesis. A brain MRI scan displayed an intraventricular lesion located in the right atrium, about 2.5cm in its major axis, homogeneously enhancing after gadolinium administration, surrounded by edema in the homolateral deep hemispheric region; the main diagnostic hypothesis was meningioma. She underwent a parieto-occipital craniotomy and a navigation-assisted posterior parietal transcortical approach, achieving complete removal of the intraventricular lesion originating from the choroid plexus. The histological diagnosis was of high-grade diffuse large B-cell lymphoma. Both an MRI scan of the entire craniospinal axis and a thoracic and abdominal CT scan showed no other neoplastic lesions; a bone marrow biopsy was normal; a final diagnosis of primary central nervous system lymphoma was made. CSF cytological analysis did not show any signs of lymphoma dissemination. Adjuvant chemotherapy with methotrexate was administered, and at the last follow-up (26 months) our patient is clinically and radiologically disease-free. Primary choroid plexus lymphoma is a very rare tumor that should be included in the differential diagnosis of intraventricular neoplasms. It usually occurs in the lateral ventricles (with a predilection for the atrium) of adult people (>50 years of age), apparently with a male prevalence. Generally, the radiological picture mimics that of a meningioma, despite the fact that meningiomas usually reach a greater volume before clinical onset. Surgery is almost always necessary to obtain an adequate tissue sample and frequently leads to a radical removal of the lesion. Low-grade marginal zone B-cell, T-cell and high-grade diffuse large B-cell (present case) forms have been described. With a proper adjuvant therapy a relatively good outcome is observed.