When is a biopsy still indicated if cerebrospinal fluid (CSF) immunohistochemistry is negative for neoplasia?

In cases where liquor immunohistochemistry is negative for neoplasia, there is still an indication for biopsy in several occasions. If clinical suspicion for a malignant process remains high despite negative immunohistochemistry, or if there are atypical cells present that cannot be fully characterized, a biopsy may be necessary for definitive diagnosis. Additionally, if the patient presents with symptoms suggestive of a specific condition, such as increased intracranial pressure, focal neurological deficits, or systemic symptoms like weight loss or fever, further investigation, including biopsy, may be warranted. A biopsy can provide tissue for more detailed histological examination and additional special studies, which can be critical in diagnosing conditions that may not have been apparent through immunohistochemistry alone. It's also important to consider the patient's overall clinical picture, including any previous history of cancer, exposure to carcinogens, or genetic predispositions, as these factors can influence the decision to proceed with a biopsy. In terms of specifics, the approach would involve discussing the risks and benefits of the procedure with the patient, obtaining informed consent, and then proceeding with the biopsy under appropriate guidance, such as imaging, to ensure safety and accuracy. Second-line interventions might include additional imaging studies or consultation with specialists in neurology, neurosurgery, or oncology, depending on the findings and the patient's condition. Ultimately, the decision to proceed with a biopsy should be made on a case-by-case basis, taking into account the potential benefits of obtaining a definitive diagnosis against the risks associated with the procedure.