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Carcinoembryonic antigen (CEA) concentrations in CSF hold promise as an indicator of metastatic leptomeningeal involvement by carcinoma.1 2 We describe a patient with leptomeningeal carcinomatosis showing a high concentration of carbohydrate antigen 19–9 (CA 19–9) but a normal CEA concentration in CSF despite equally positive immunostaining in the cytoplasm of tumour cells in CSF.
A 44 year old man was admitted complaining of headaches and diplopia over 3 months. Neurologically, the patient was alert despite neck stiffness. Multiple cranial nerve dysfunction was apparent, specifically bilateral lateral gaze palsy, inability to move his jaw due to masseter palsy, facial diplegia, left soft palate weakness, and absence of gag reflex on the left. Four limb ataxia was evident, and his gait was wide based and unsteady. Reflexes were symmetrically hypoactive in all extremities and pathological reflexes were absent.
Chest CT disclosed nodular, contrast enhancing, left upper lung densities. Gastric fibroscopy and abdominal CT were unrevealing. Non-contrast brain MRI was normal. On lumbar puncture, opening pressure was high (160 mm H2O). His CSF was xanthochromic and contained 9 cells/mm3, 117 mg/dl protein, and 48 mg/dl glucose. Cytological examination of CSF disclosed scattered large cells with irregularly shaped, polymorphic nuclei, sometimes with large cytoplasmic vacuoles characteristic of adenocarcinoma (fig 1 A, B). The CEA concentration (radioimmunoassay: Eiken, Tokyo, Japan) in CSF remained low (1.1 ng/ml), unlike that in serum (81.1 ng/ml (upper normal limit 2.5 ng/ml)). By contrast, the CSF concentration of CA 19–9 (enzyme immunoassay: Dainabot, Tokyo, Japan) was extremely high (61.4 U/ml), whereas that in serum remained nearly normal (39.4 U/ml (upper limit 37 U/ml)).
Weekly intrathecal methotrexate administration (10 mg) for 5 weeks failed to improve neurological deficits or lower CSF CA 19–9 concentrations (fig 2). Subsequently treatment was changed to weekly intrathecal cytarabine (30 mg) for 6 weeks, adding brainstem radiotherapy for the last 2 weeks. Headache and neck stiffness were relieved. The cranial nerve palsies and four limb ataxia remained unchanged.
Repeat CSF analysis disclosed the disappearance of identifiable tumour cells and a marked decrease in CSF CA 19–9 concentration, from 78.9 to 16.4 U/ml, whereas that of CEA in CSF remained at its previous low concentrations despite continuing high CEA in serum. Two weeks later, the patient became deaf and confused. Concentrations of CA 19–9 increased in the CSF, and the patient died 26 weeks after admission. Permission for postmortem examination was withheld.
Immunocytochemical studies of tumour cells in the CSF from the patient and two control patients with leptomeningeal carcinomatosis from squamous cell lung cancer in whom CEA concentrations in serum and CSF were normal or negative were performed as follows. Cells obtained from CSF at initial lumbar puncture were collected on slides using cytospin equipment. Cell preparations were stained using monoclonal antibodies against CA 19–9 or CEA (Lipshaw, Detroit, MI, USA), both of which were labelled with peroxidase by the avidin-biotin complex method. For this staining, slides were fixed in acetone, air dried, and washed for 30 minutes in three changes of phosphate buffered saline (PBS). Additional PBS washes (15 minutes in three changes) were interposed between the following steps. After the slides were incubated at 37°C for 20 minutes with monoclonal mouse primary antibody, they were incubated at 37°C for 20 minutes with biotinylated secondary antibody. After this the slides were placed for 10 minutes in PBS with 1.5% hydrogen peroxide and then incubated in avidin-biotin complex solution at 37°C for 20 minutes. After incubation for 5 minutes with diaminobenzidine (0.5 mg/ml) as substrate and hydrogen peroxide (0.3%) in PBS, the slides were counterstained with haematoxylin. The cytoplasm of the tumour cells was strongly positive for both CA 19–9 and CEA, indicating production of the markers by the cells (fig 1 C, D). Tumour cells in CSF from the two control patients with squamous lung cancer were immunocytochemically negative for CEA, arguing against false positive staining in the patient.
On the assumption that tumour markers with a molecular weight similar to that of IgG should have similar filtration transfer properties at the blood-CSF barrier, the portion of tumour marker (CA 19–9) produced was calculated in relation to IgG according to the equation1 Ca 19–9 loc (U/ml) was 59.6 initially, 7.4 at 18 weeks later, and 57.5 at 26 weeks after admission.
CA 19–9 is a monoclonal antibody defined carbohydrate antigen3 expressed by many carcinomas, which is useful for carcinoma detection, mainly in the digestive tract4 but sometimes in lung adenocarcinoma.5
The present patient high CSF CA 19–9 concentration, in whom leptomeningeal carcinomatosis probably originated from lung carcinoma, raised two new issues. Firstly, this is the first report in which CSF concentrations of CA 19–9 but not those of CEA proved useful as a marker in leptomeningeal carcinomatosis. The case showed a high CSF/serum CA 19–9 ratio of 1.56 (61.4 U/ml/39.4 U/ml), indicating that the marker was produced and released by meningeal tumour cells. In addition to the evidence from calculations demonstrating local production of CA 19–9, tumour cells in CSF were shown to possess CA 19–9-producing ability by cytoplasmic immunostaining. Therefore, serial determinations of CA 19–9 concentration in CSF may be helpful in the diagnosis and clinical management of leptomeningeal carcinomatosis even when the CEA concentration in CSF is not increased.
The second point of interest is that the CEA concentration was not increased throughout the clinical course despite increases in serum, and despite CEA immunoreactivity in the cytoplasm of tumour cells in the CSF. This discrepancy indicates that CEA produced by tumour cells in the meninges was not effectively released into CSF, for unknown reasons. However, determination of both CEA and CA 19–9 concentrations in CSF may increase sensitivity and effectiveness of tumour markers in the diagnosis and monitoring of leptomeningeal carcinomatosis, as one may be raised in isolation.
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