Involvement of the central nervous system in malignant lymphomas.

A retrospective histologic study of 145 consecutive autopsy cases of systemic malignant lymphomas (including lymphatic leukemias) was performed. The classification followed the Kiel Classification (Gérard-Marchant et al., 1974). There was an overall secondary CNS involvement in 26.2% of the total or in 30.4% of the non-Hodgkin's lymphomas including ALL, with intracranial lesions in 21.4 and 26.1%, respectively, and spinal epidural spread in 5.5 (5.1%). Peripheral nerve involvement was seen in almost 40% of the examined cases. Ten further cases were isolated ("primary") intracranial lymphomas without evidence of extraneural deposits or systemic lymphatic disease. The CNS complications in non-Hodgkin's lymphomas were diffuse meningeal and/or perivascular infiltration with or without invasion of the nervous parenchyma, and did not differ from those in CNS leukemia. Isolated solid mass lesions in the brain were only present in 7% of the secondary CNS lymphomas, but were seen in all instances of "primary" cerebral lymphomas. The incidence of CNS complications was highest in lymphoblastic lymphomas including ALL (39%), CLL (31%), immunocytic lymphoma (29%), less frequent in immunoblastic (18.7%), and centrocytic lymphomas (16.6%). No intracranial lesion was observed in centroblastic-centrocytic and centroblastic lymphomas which only produced epidural spread. Bone marrow involvement was present in 92.8% of the cases with secondary CNS lesions, and in 83.2% of the epidural lymphomas. Leukemic conversion, present in 44% of the total (52% with ALL), was demonstrated in 83.3% of the cases with secondary brain lesions, but was hardly combined with epidural spread. The histologic pattern of CNS lesions in non-Hodgkin's lymphomas and their frequent association with leukemic conversion suggest the importance of hematogenous dissemination rather than of direct spread from bone marrow or local manifestation in multisystem disease. Isolated ("primary") lymphomas of the CNS which are morphologically identical with the extraneural lymphomas may represent a primary, often lethal manifestation of a multisystem disease with or without secondary generalization.