1-5 Cerebrospinal Fluid (CSF)
Contents
- Ivan Chebib MD, Amy Ly MD, Ron Arpin SCT
- Reading: Cibas 4th Ed. Chapter 6; Bibbo/Wilbur 4th Ed. Chapter 16
- Questions: When you have completed unit 1-5 go to the Assessment tab and answer the question.
- Dr. Tambouret CSF Lecture
- Indications for cytology examination
- Procuring the specimen
- Test platforms/specimen processing and triage
- Reporting and terminology
Introduction
CSF is produced by the choroid plexus in lateral, 3rd and 4th venticles by passive filtration and active transport. The CSF circulates through the subarachnoid space from the ventricles to bathe the brain and spinal cord. The Chorioid plexus consists of frond-like villous projections of vessels and pia mater that protrude into the ventricles. Specialized ependymal cells known as choroidal epithelium overlies the villi. The CSF is resorbed in the archanoid villi in the superior sagittal and intracranial venous sinuses and around spinal nerve roots. The arachnoid villi function as one way valves.
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Indications for cytology examination
The CSF is examined in many clinical situations. The CSF is submitted for cytology examination usually only when a malignancy is suspected, either metastatic solid tumors or lymphoma/leukemia. Leptomeningeal (LM) metastasis is diagnosed in about 5% of patients with metastatic carcinoma. The tumors most likely to involve the CSF in order of frequency are breast, lung, melanoma, GI tumors and carcinoma of unknown primary. Primary brain tumors can involve the CSF. Forty percent of primary CNS lymphomas will have LM involvement
Accuracy
The sensitivity of CSF cytology for malignancy ranges from 80 to 95%. False-positive results are very rare, but false negative (FN) results are not uncommon. To minimize FN a minimum of 10 cc CSF should be sent to cytology, the sample should be processed promptly and a repeat sample obtained if malignancy suspected but results are negative. One study showed increasing sensitivity with repeat samples of 71% for first, 86% for second, 90% for third and 98% for > 3 samples (Glantz MJ et al. Cancer 1998;82:733).
Procuring the CSF sample
Usually the CSF is obtained by lumbar puncture. Samples may also be obtained from an Ommaya resevoir which consists of a subcutaneous pouch connected to a cannula ending in one of the lateral ventricles.
Test platforms/specimen processing and triage
Currently in the MGH lab two cytospin slides are prepared from a fresh CSF sample. One slide is fixed in 95% ethanol immediately after preparation and stained with Papanicolaou stain. The second is allowed to air dry and then is stained with rapid Giemsa stain used at MGH.
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The CSF Cytology Report
The results are report as one of four categories: Negative for malignant cells, Atypical (low degree of suspicion for malignancy), Suspicious (a high degree of suspicion for malignancy) or Positive for malignant cells. Over 90% of CSF samples are reported as Negative.
Basic cytomorphology
- Rare lymphocytes, monocytes and PMN's
- Occasionally, ependymal cells, arachnoidal cells and choroid plexus cells are found
- Squamous cells, chondrocytes and red blood cells may be found as contaminants
- Singly distributed, usually monomorphic population of cells with high N:C ratio
- Nuclei are irregular with clumped chromatin
- Macronucleoli may be present
- Mitotic activity may be evident
- Cells are usually singly distributed with occasional loose clusters
- Nuclei are round to oval, centrally or eccentrically located and may be multiple
- Nuclear chromatin is vesicular with eosinophilic macronucleoli
- Coarse, brown melanin granules may be present within the cytoplasm
- Adenocarcinoma - cells are present singly or in small clusters
- Nuclei are irregular, three dimensional and eccentrically located
- Nucleoli are often present
- May be cytoplasmic vacuolization
- Small cell carcinoma - cells are present in small, molded groups
- Nuclei exhibit classic salt and pepper chromatin pattern and may be angular
- Cells have only a scant rim of fragile cytoplasm
