Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (102 page)

BRAIN TUMOR

   Definition

Brain tumors are a diverse group of neoplasms, both malignant and benign, with varying growth rates and symptoms. A large number of mass lesions within the intracranial vault are metastatic, arising from malignancies in other organs, or hematologic (leukemia or lymphoma).

   Clinical Presentation

Patients may present with headache, seizure, nausea and vomiting, syncope, cogni-tive dysfunction, weakness, loss of sensation, and aphasia. Suspicion for intracranial neoplasm should be followed by neurologic testing and neuroimaging including CT, MRI, PET, and single-photon emission computed tomography (SPECT) scanning.
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Definitive diagnosis of an intracranial mass lesion is made on biopsy. Frozensection or smear evaluation of tumoral tissue can be made in the operating room, which will allow the neurosurgeon to proceed with definitive resection if possible (see eBook Figure 4-19).

   Laboratory Findings

Evaluation of the CSF may help in the diagnosis. The CSF is usually clear, but it may occasionally reveal xanthochromia or be frankly bloody if there is hemorrhage into the tumor. The WBC count may be increased ≤150 cells/μL in up to 75% of patients and normal in others. Protein is usually increased. Protein is particularly increased with meningioma of the olfactory groove and with acoustic neuroma.

Tumor cells may be demonstrable in up to 40% of patients with all types of solid tumors, but failure to find malignant cells does not exclude neoplasm.
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Atypical WBCs may be seen in leukemia or lymphoma. Tumor antigens/markers may indicate the source of some metastatic tumors. Glucose may be decreased if cells are present. Oligoclonal bands may be present in patients with tumor and are nonspecific.

Brain stem gliomas, which are characteristically found in childhood, are usually associated with normal CSF. The CSF is usually normal in “diencephalic syndrome” of infants due to glioma of the hypothalamus.

References

1.  Sun D, Liu Q, Liu W, et al. Clinical application of 201Tl SPECT imaging of brain tumors.
J Nucl Med.
2000;41:5.

2.  Marton KI, Gean AD. The spinal tap: a new look at an old test.
Ann Intern Med.
1986; 104:840.

GLOMUS JUGULARE TUMOR (JUGULOTYMPANIC PARAGANGLIOMA)

   Definition

This tumor arises from the jugular and tympanic paraganglia within the ear and is the most common tumor of the middle ear.
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It is a slow-growing, vascular tumor, with blood supply from the external and/or internal carotid artery.

   Clinical Presentation

It is most common in women and may result in hearing loss with pulsing/ringing in the ear, dizziness, and ear pain.

   Laboratory Findings

The diagnosis is made by neurophysiologic testing and CT or MRI. Blood and urine tests for endocrine workup (urinary and/or plasma fractionated metanephrines and catechol amines) should be performed. Evaluation of the CSF may reveal an increase in protein.

Reference

1.  Michaels L, Soucek S, Beale T, et al. Jugulotympanic paraganglioma. In: Barnes L, Eveson JW, Reichart P, Sidransky D, eds.
World Health Organization Classification of Tumours. Pathology and Genetics Head and Neck Tumours
. Lyon, France: IARC Press; 2005:362–366.

LEUKEMIC INVOLVEMENT OF THE CENTRAL NERVOUS SYSTEM

See Chapter
9
, Hematologic Disorders.

   Laboratory Findings

Intracranial hemorrhage is the principal cause of death in leukemia (may be intracerebral, subarachnoid, or subdural). It is more frequent when the WBC count is >100,000/μL and with rapid increases in the WBC count, especially in blast crises. The platelet count is frequently decreased. Often there is evidence of bleeding elsewhere. At autopsy, the tumor may be identified in the arachnoid, meninges, and perivascular regions (see eBook Figure 4-20).

Evaluation of the CSF may be diagnostic. There may be intracranial hemorrhage and infiltration of leukemic cells into the meninges and fluid. The CNS is involved in 5% of patients with ALL at diagnosis and is the major site of relapse. PCR is used to detect minimal residual cells that are not recognized morphologically. Involvement of the CSF by AML is less common than ALL and CLL, and plasmacytoid leukemias are very rare.
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The CSF may show an increased opening pressure and protein level. The glucose may be decreased to <50% of the blood level. Abnormal cells may be identified by cytochemical, immunohistochemical, immunofluorescent, or flow cytometric techniques to help diagnose leukemia. Malignant cells are found in 60–80% of patients with meningeal involvement.
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Evaluation of the CSF may also help in identifying complicating meningeal infection (e.g., various bacteria, opportunistic fungi).

References

1.  Peterson BA, Brunning RD, Bloomfield CD, et al. Central nervous system involvement in acute nonlymphocytic leukemia. A prospective study of adults in remission.
Am J Med.
1987;83:464.

2.  Shihadeh F, Reed V, Faderl S, et al. Cytogenetic profile of patients with acute myeloid leukemia and central nervous system disease.
Cancer.
2012;118:112.

LYMPHOMATOUS INVOLVEMENT OF THE CENTRAL NERVOUS SYSTEM

See Chapter
9
, Hematologic Diseases.

   Laboratory Findings