Excludes1 pair
C37 vs C49.3
C37 and C49.3 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported.
The official note, declared on C49.3
malignant neoplasm of thymus (C37)
C37
Malignant neoplasm of thymus
Billable
- Chapter 2
- Neoplasms
- Section
- C30-C39
Indexed under
- Carcinoma › thymic
- Thymoma › malignant
- Thymoma › metaplastic
- Thymoma › sclerosing
- Thymoma › type A
C49.3
Malignant neoplasm of connective and soft tissue of thorax
Billable
- Chapter 2
- Neoplasms
- Section
- C45-C49
Use when the record says
- Malignant neoplasm of axilla
- Malignant neoplasm of diaphragm
- Malignant neoplasm of great vessels
Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027