Is C79 a billable ICD-10-CM code?

No. C79 is a non-billable header code. Code to a higher level of specificity using one of its child codes.

Where does C79 sit in the tabular list?

Neoplasms (C00-D49), in the block Malignant neoplasms of ill-defined, other secondary and unspecified sites (C76-C80).

What cannot be coded together with C79?

C79 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.

C79

C79 — Secondary malignant neoplasm of other and unspecified sites

Non-billable headerICD-10-CM

C79 is a non-billable header ICD-10-CM code for secondary malignant neoplasm of other and unspecified sites. It cannot be billed on its own: choose one of the more specific child codes below.

Excludes1 — never code together

These conditions cannot occur together. Billing both on the same encounter is a denial.

secondary carcinoid tumors (C7B.-)
secondary neuroendocrine tumors (C7B.-)

Other codes that can never be billed with C79

These codes carry an Excludes1 note pointing at C79. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading C79 alone.

C80.1Malignant (primary) neoplasm, unspecified

Risk adjustment

C79 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.

Code to one of these instead C79

10 child codes. Green means billable.

Questions about C79

Is C79 a billable ICD-10-CM code?: No. C79 is a non-billable header code. Code to a higher level of specificity using one of its child codes.
Where does C79 sit in the tabular list?: Neoplasms (C00-D49), in the block Malignant neoplasms of ill-defined, other secondary and unspecified sites (C76-C80).
What cannot be coded together with C79?: C79 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.