Cartilage Cells - A Potential Mimicker of Malignant Cells in Cerebrospinal Fluid and a Diagnostic Pitfall.

Sir,

Cartilage cells can be seen rarely as contaminants in cerebrospinal fluid (CSF). Their presence may result in an erroneous cytological diagnosis of malignancy. Unnecessary investigations following the misdiagnosis would add to the anxiety and financial burden to the patient. Due to its uncommon occurrence, very few case reports have been found in literature. Most of the textbooks mentioning the presence of cartilage in CSF have limited photographs illustrating the same. Takeda et al.[1] reported cartilage cells in 6 (0.2%) of 3200 CSF specimens. With the aim to alert cytopathologists about this diagnostic pitfall, we report a recent case of CSF contamination by cartilage cells in a 31-year-old patient.

A 31-year-old male, a known diabetic, presented to the triage with complaints of fever, headache, shortness of breath, and altered sensorium. He was a known case of disc bulge in L5/S1 region. On examination, his vitals were normal. On neurology examination, he was found to have weakness in the right upper and lower limbs. A provisional clinical diagnosis of acute inflammatory demyelinating polyneuropathy was made.

A lumbar puncture (LP) was performed under aseptic conditions and sent for cell count, cell type, biochemistry, and cytology for malignant cells. Cytology slides were prepared after cytocentrifugation, and both air-dried and wet (alcohol) fixed preparation were made. These slides were then stained with May–Grünwald–Giemsa (MGG) and Papanicolaou (Pap) stains, respectively.

On microscopic examination, smears stained with Pap stain were cellular, consisting of large cells in clusters and scattered singly. These cells had a pyknotic nucleus and moderate amount of purplish cytoplasm in Pap stain [Figure 1a and b]. Few binucleated forms were also noted. MGG-stained smears were dominated by a magenta colored ground substance [Figure 1c]. No leucocytes were seen in the smears. On seeing the cellularity of smears and large cells, malignancy was considered as a strong differential. Imaging studies were then revisited, and magnetic resonance imaging brain and spine revealed patchy nonspecific marrow edema in D11 and part of D12 vertebra; however, no intracranial lesion was seen. In view of the discrepant cytoradiological findings, the slides were reviewed. The large cells were found to resemble chondrocytes associated with magenta colored ground substance. So a final diagnosis of CSF contamination by chondrocytes was given and a repeat sampling advised.

Figure 1

(a) Cartilage cells with round to pyknotic nuclei and purplish cytoplasm with associated purplish ground substance (Pap, ×1000). (b) Binucleate cartilage cells (Pap, ×1000). (c) Abundant magenta colored ground substance. Cellular details are not seen (MGG, ×1000)

Examination of CSF for the presence of cells provides useful information in many diseases of the central nervous system.[2] It is important to be aware of the cellular components of the various tissue layers between the skin and subarachnoid space to diagnose potential contaminants that may appear in CSF samples. Cells which are found en route of the CSF aspiration needle can sometimes be observed in CSF. If the LP needle is inserted too far anteriorly, CSF can be contaminated by chondrocytes or bone marrow cells from the intervertebral disc or vertebral body, respectively.[3] Other non-neoplastic cellular elements that may be seen in the CSF include squamous cells, meningothelial cells, brain fragments, choroidal cells, ependymal cells, and hematopoietic elements from bone marrow or peripheral blood.[34] When cartilage cells are encountered in the CSF, chordoma and metastatic tumors such as liposarcoma and renal cell carcinoma have to be considered.[5] A cytologist should be aware of the presence and morphology of these extraneous cells as they are potential mimickers of malignancy.

To conclude, this case is highlighted to alert cytopathologists to the presence of extraneous cartilage in CSF which is a potential mimicker of malignancy and thus a diagnostic pitfall.

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Conflicts of interest

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