Wiki ICD-9 for malignant CSF

For malignant CSF only without mention of Carcinoma, I will use 792.0 and if carcinoma is confirm, use 199.1. If a specific site is given, code to malignancy of the site. Hope this helps...
I don't think you have anough information to accurately select a code, with only "malignant CSF"; I searched the term online, and found a lot of info pointing to meningitis, which can be cancerous, bacterial, or viral - here's a couple of examples:
Cerebrospinal fluid (CSF) cytology: current status and diagnostic applications.
Bigner SH.
SourceDepartment of Pathology, Duke University Medical Center, Durham, NC 27710.

Cytologic evaluation of cerebrospinal fluid (CSF) is an effective means for diagnosing many disorders involving the central nervous system (CNS). Interpretation of these samples requires an understanding of the spectrum of neurologic diseases which involves the subarachnoid space, either primarily or secondarily, as well as familiarity with the cytologic characteristics of these lesions. Here the clinical features and cytologic presentation of common conditions which can be diagnosed by CSF cytology are reviewed. Preparatory methods for CSF examination are discussed and normal and reactive conditions involving CSF, lymphoma, leukemia, meningeal carcinomatosis and the subarachnoid spread of primary brain tumors are described and illustrated.

I'd definitely get clarification from the provider as to what they meant by "malignant CSF', and maybe see if codes from 322.0 - 322.9 are applicable. Other codes worth considering might be 036.0 (Cerebrospinal meningitis); 047.0 - 047.9 (viral meningiitis); & 198.4 (carcinomatous meningitis)

Without clarification, I would lean towards 349.9, which I found indexed under "Diseased cerebrospinal".

I don't think that 792.0 (Abnormal CSF), goes quite far enough - yes, it is abnormal, but it's more than that - it's harmful. I'd be interested to know what you find out, though. Hope that helps! ;)

You are right, there is not enough information to arrive to a most accurate Diagnosis code, in most cases in Pathology, you don't get enough clinical information to properly assign a diagnosis, especially in cases in which the specimen came from an outside laboratory. Even the Pathologist does not have the access to the clinical information in some of the specimen they are examining. That is why, I can not stress more the importance of clinical data in Pathology coding. I chose 792.0 for the reason that the CSF is abnormal, and due to lack of Specificity in ICD-9, for a malignant CSF, then the malignant is abnormal. You are right, Malignant CSF is harmful, that is why, it warrants for an additional study like Flow Cytometry to assess the hematopoietic tissue for Lymphoma or Leukemia, Molecular Diagnostic to identify infection, like Meningitis, Bacteria, Fungi and parasites. and Surgical Pathology to identify Tumor and it's origin. Malignant does not necessarily means Neoplasm unless confirm by the Pathologist, but it is harmful to the patient.I suggest that if you have those documentation from additional study, then wait until the result is establish to code the CSF cytopathology, if not assigning 792.0 would be appropriate if nothing else. Just my opinion.

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