Wiki Metastatic Cancer


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I'm a new pathology coder without internal resources to consult and I'd appreciate if anyone could help me out with this - I am getting several clinical histories of "metastatic lung adenocarcinoma" and "metastatic squamous carcinoma", and very limited supporting paperwork. Am I to assume that the cancer to which they are referring should be coded as secondary or primary? For example, in the first scenario, would I use 162.9 for primary malignant neoplasm of lung, assuming it has metastisized to another location or 197.0 for secondary malignant neoplasm of lung, assuming that it is a cancer that has metastisized to the lung?

Thanks for any help!
coding clinic May-June 1985 actually has a great answer to this. Some sites are more common as primary and some are more common as secondary. If the diagnosis is vague as you have state then if it is a common primary site like the lung then code the lung as primary with unknown secondary (199.1)
If the site is more common as a secondary such as liver then code the primary as unknown (199.1) and the site as the metastatic.
So in your example you would code the metastatic lung adenocarcinoma as a 162.9 and a 199.1
the metastatic squamous carcinoma is really not enough for a primary unless it is skin so 199.1
199.1 is a code used for either unknown primary or unknown secondary