Malignant Non-Hodgkin Lymphoma
Characteristics. Malignant non-Hodgkin lymphomas (NHL) are primary intracerebral lymphomas, also called primary central nervous system lymphomas (PCNSL). They now constitute 4–7% of all primary brain tumors, and the incidence is increasing. More than 98% of them are B-cell lymphomas, and according to the Revised European–American Lymphoma (REAL) classification, they are predominantly diffuse large-cell lymphomas. The presence of the Epstein-Barr virus (the EBV genome is detected in > 95% of cases) and immunosuppression (in AIDS patients, or after organ transplantation) promote the occurrence of PCNSL. In immunocompetent patients, the age peak appears in the 6th and 7th decades of life (male:female ratio 3:2); in immunosuppressed patients it is considerably earlier. Clinically, PCNSL manifest with focal neurological deficits, signs of elevated intracranial pressure, and psychopathological abnormalities.
Diagnosis. The suspected diagnosis is established by CT and MRI and is supported by spectroscopy. Confirmation of the diagnosis requires detection of lymphoblasts. However, at first diagnosis of a PCNSL lymphoblasts are found in the CSF in less than 50% of patients (Balmaceda et al., 1995). If the cytomorphology is not unambiguous, immunocytochemistry and clonality analysis may help to strengthen the diagnosis (Storch-Hagenlocher et al., 2000). If doubts still remain regarding the CSF analysis, brain biopsy must be performed to confirm the diagnosis.
Leptomeningeal metastasis occurs particularly in acute leukemia, the lymphoblastic type more often (about 15% of adults) than the myelogenous type. Recurrences of acute lymphoblastic leukemia (ALL) are often primarily leptomeningeal. As with lymphomatous meningitis, a definite diagnosisrequires CSF collectionwithout blood contamination.
Fig. 16.6 Lymphoblastic crisis in non-Hodgkin lymphoma.
Leptomeningeal metastases of a primary extraneural lymphoma have been described in 10–30% of cases. In by far the majority of cases the underlying disease is NHL, particularly highly malignant NHL and Burkitt's lymphoma. CSF analysis, in addition to CT and MRI, plays an important role in confirming the diagnosis of leptomeningeal lymphomatous spread.
The diagnosis of lymphomatous meningitis may create considerable problems at cytomorphologic assessment. It is often accompanied by an inflammatory reaction, and the transformed lymphocytes are often difficult to distinguish from neoplastic cells. However, a highly homogenous cell population associated with pathological neurochemical findings is regarded as indicating meningeal spread.
Cytomorphologically, the diagnosis of lymphomatous meningitis can be difficult because of a concomitant reactive inflammatory reaction.
Morphology. The cytomorphological criteria of malignancy apply (Figs. 16.6, 16.7). Occasionally, staghorn or cloverleaf nuclei are found.
Immunological diagnosis. For immunological typing of leukocytes, membrane-bound or intracellular antigens are detected in the cytospin preparation using specific monoclonal antibodies. The cellular antigens expressed are designated as clusters of differentiation (CD) and are numbered. They can thus be assigned to the B-cell line (e. g., CD 19, CD 20), the T-cell line (e. g., CD 4, CD 8), or the myeloid cell line of leukocyte differentiation (e. g., CD 13), and also to the stage of cell maturation (Fig. 16.8).
For preference, cytospin preparations are analyzed using the immunoenzyme technique. The primary monoclonal antibody binds to cells expressing the antigen for which it has specificity. Binding of this antibody is made visible using a second antibody linked to an enzyme (peroxidase, alkaline phosphatase) that catalyzes the cytochemical staining.
Fig. 16.7 a, b Primary central nervous system lymphoma (PCNSL).
Fig. 16.8 Immunocytochemistry of PCNSL: positive staining of a B lymphoblast for CD 20 antigen.
The direct immunofluorescence technique is used to study CSF cells in suspension. For this purpose, the specific primary antibody is coupled with a fluorescence dye. Using different fluorochromes, several antibodies can be used simultaneously, and the cells are then analyzed by fluorescence-activated cell sorting (FACS). However, this method is limited in its usefulness as the quantity of CSF available is often insufficient.
Clonality analysis. Molecular clonality studies can confirm a diagnosis of lymphomatous or leukemic meningitis when the cytomorphology remains unclear. The nuclear DNA from CSF cells is used as the starting material. The CDR3 region of the immunoglobulin heavy chain (IgH) is selectively amplified by PCR. The highly variable CDR3 region is specific for every B-cell clone and is formed during B-cell maturation by rearrangement of various segments of the IgH genes (Fig. 16.9 a). Further analysis of the PCR products by automated fluorescence analysis may detect a monoclonal neoplastic B-cell population (Fig. 16.9 b).
Molecular analysis of CSF cells (clonality analysis) may confirm the diagnosis of lymphomatous and leukemic meningitis.
Elevated total protein and CSF lactate levels together with a low CSF glucose level are typical signs of meningeal infiltration. The specificity of soluble surface markers (e. g., sCD 25) is not sufficient. Intrathecal IgM production may indicate a lymphoma (Fig. 19.4 d).
Serum analysis. Serum tests are important to detect blood–CSF barrier dysfunction and intrathecal immunoglobulin production.
There are no specific diagnostic serum markers of lymphoma or leukemia. Serum albumin is often decreased. Elevated β2-microglobulin and/or LDH levels may indicate meningeal infiltration. β2-Microglobulin is detected in the serum by immunoassay: values above 4.0 mg/L are pathological.
Fig. 16.9 a, b Molecular analysis of B cells and detection of monoclonal populations.
a B cell maturation. Somatic recombination leads to a clone-specific VDJ sequence (CDR3 region) serving as the target sequence for PCR.
b Monoclonal cell populations in lymphomatous meningitis.
Balmaceda C, Gaynor JJ, Sun M, et al. Leptomeningeal tumor in primary central nervous lymphoma: recognition, significance, and implication. Ann Neurol 1995;38:202–209
Chhieng DC, Elgert P, Cohen JM, et al. Cytology of primary central nervous system neoplasms in cerebrospinal fluid specimens. Diagn Cytopathol 2002;26:209–212
Fleischhack G, Bode U. Tumoren des Nervensystems im Kindesalter. In: Schlegel U, Weller M, Westphal M, eds. Neuroonkologie. Stuttgart: Thieme; 2003
Fouladi M, Gajjar A, Boyett JM, et al. Comparison of CSF cytology and spinal magnetic resonance imaging in the detection of leptomeningeal disease in pediatric medulloblastoma or primitive neuroectodermal tumor. J Clin Oncol 1999;17:3234–3237
Gajjar A, Fouladi M, Walter AW, et al. Comparison of lumbar and shunt cerebrospinal fluid specimens for cytologic detection of leptomeningeal disease in pediatric patients with brain tumors. J Clin Oncol 1999;17:1825–1828
Gupta RK, Naran S, Lallu S, Fauck R. Cytodiagnosis of neoplasms of the central nervous system in cerebrospinal fluid samples with an application of selective immunostains in differentiation. Cytopathology 2004;15:38–43
Kaplan JG, DeSouza TG, Farkash A, et al. Leptomeningeal metastases: comparison of clinical features and laboratory data of solid tumors, lymphomas and leukemias. J Neurooncol 1990;9:225–229
Kluge H, Wieczorek V, Linke E, Zimmermann K, Isenmann S, Witte OW (eds). Atlas of CSF Cytology. Stuttgart: Thieme; 2006
Meyers SP, Wildenhain SL, Chang JK, et al. Postoperative evaluation for disseminated medulloblastoma involving the spine: contrast-enhanced MR findings, CSF cytologic analysis, timing of disease occurrence, and patient outcomes. AJNR Am J Neuroradiol 2000;21:1757–1765
Posner JB. Leptomeningeal metastases. In: Posner JB, ed. Neurologic complications of cancer. Philadelphia: FA Davis; 1995:143–171
Schackert, G, Schlegel U. Metastatische Gehirntumoren. In: Schlegel U, Weller M, Westphal M, eds. Neuroonkologie. Stuttgart: Thieme; 2003
Storch-Hagenlocher B, Haas J, Vogt-Schaden ME, et al. Molecular analysis of the CDR3 encoding region of the immunoglobulin heavy chain locus in cerebrospinal fluid cells as a diagnostic tool in lymphomatous meningitis. Ann Neurol 2000;47:211–217
Jellinger K, Grisold W, Weiss R. Zytologische Differenzierung von Malignomzellen des Liquor cerebrospinalis. In: Kölmel HW, ed. Zytologie des Liquor cerebrospinalis. Weinheim: VCH; 1986
Thomas L. Labor und Diagnose. 6th ed. Frankfurt am Main: TH Books; 2005
Winkler D. Pinealistumoren. In: Schlegel U, Weller M, Westphal M, eds. Neuroonkologie. Stuttgart: Thieme; 2003