ICD-10-CM 2027 diagnosis code

C66Malignant neoplasm of ureter

Not billable — use a more specific code

C66 is a header code, so it can't be reported by itself. Choose one of the 3 more specific codes beneath it.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About C66

C66 is the ICD-10-CM diagnosis code for malignant neoplasm of ureter. It belongs to block C64-C68 (malignant neoplasms of urinary tract) and chapter 2 (neoplasms). It is a header code, so it can't be reported by itself; one of its 3 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: C66.1 (ureter), C66.2 (ureter) and C66.9 (ureter).

Don't report C66 together with the conditions in its Excludes1 note: malignant neoplasm of ureteric orifice of bladder (C67.6).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under C66

Coding notes

Excludes1Not coded here — never report together with this code

malignant neoplasm of ureteric orifice of bladder (C67.6)

Notes that apply from higher levels

Instructions written at a parent level also apply to C66.

Broader instructions also apply from Chapter 2: Neoplasms.

Table of Drugs & Neoplasms entries

Neoplasm, neoplastic › ureter, ureteral — Malignant Primary

Code history

2016
2017
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2021
2022
2023
2024
2025
2026
2027

FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
No changes since FY2016.

Common questions about C66

Is C66 billable?: No. C66 is a header code. Report one of its more specific subcodes instead.