Diagnosis of lymphoma, leukemia, and metastatic tumor involvement of the cerebrospinal fluid by cytology and immunocytochemistry.

Fifty-five cerebrospinal fluid (CSF) specimens from 42 patients with suspected meningeal tumor involvement were reviewed. Cytology in conjunction with immunocytochemistry identified 26 CSF specimens as malignant. There were fifteen cases of lymphoma, four cases of leukemia, two cases of carcinoma, and two cases of melanoma. A monoclonal light chain expression was demonstrated in nine out of eleven B cell lymphomas. The three T-cell lymphomas all expressed pan T markers (CD 3) and two the T-helper antigen (CD 4). One patient had meningeal involvement of a true histiocytic lymphoma which was identified by its large atypical cells which were positive for alpha-1-anti-trypsin and muramidase. In four patients with a primary diagnosis of acute lymphoblastic leukemia, CSF involvement was confirmed by the demonstration of blasts with CD 10 (cALLA) or light chain restriction. Epithelial or melanocytic markers were demonstrated on the tumor cells in CSF from the remaining four patients. In 29 CSF specimens a diagnosis of reactive lymphocytosis was made using cytomorphology which mostly was characterized by macrophages mixed with small mature lymphoid cells. Immunologic evaluation showed that these mature cells were CD 10 negative T-cells and only few specimens contained polyclonal B-cells. The subsequent clinical course of these patients showed no evidence of CNS malignancy. It is concluded that cytology should be used in conjunction with immunocytochemistry to accurately evaluate CSF specimens from patients with possible malignant meningitis.