2027 ICD-10-CM Diagnosis Code C7A.1Malignant poorly differentiated neuroendocrine tumors
ICD-10-CM Codes›C00–D49›C7A›C7A
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 21
- Chronic Condition
C7A.1 is a billable ICD-10-CM diagnosis code for malignant poorly differentiated neuroendocrine tumors. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 826 through 830, 843 through 845. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 38 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Malignant neuroendocrine tumors.
For Medicare Advantage risk adjustment, C7A.1 maps to CMS-HCC Category 21 (Lymphoma and Other Cancers) under the V28 model, adding a risk factor of about 0.671 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
C7A.1 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to C7A.1: its own notes plus those printed at C7A and Chapter 2. A note printed at a category, block or chapter applies to every code under it.
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Malignant poorly differentiated neuroendocrine tumor NOS
- Malignant poorly differentiated neuroendocrine carcinoma, any site
- High grade neuroendocrine carcinoma, any site
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Use Additional Code
Add a second code, after this one, to fully describe the condition.
Code Also
A second code may be needed to fully describe the condition; the note gives no sequencing direction.
Notes
General instructions on how these codes are used.
- Functional activity
- All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
- Morphology [Histology]
- Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
- Primary malignant neoplasms overlapping site boundaries
- A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
- Malignant neoplasm of ectopic tissue
- Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name C7A.1, its category, or a range that includes it.
Excludes1 1
These codes carry an Excludes1 note naming C7A.1: they are not reported together with it, unless the two conditions are unrelated.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Carcinoma (malignant) See Also: Neoplasm, by site, malignant;
neuroendocrine See Also: Tumor, neuroendocrine;
high grade, any site C7A.1
Tumor See Also: Neoplasm, unspecified behavior, by site;
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Neuroendocrine Carcinoma
an aggressive carcinoma composed of malignant cells that exhibit neuroendocrine differentiation. it is classified as small cell or large cell neuroendocrine carcinoma.
Patient EducationClinical
Cancer
Cancer is not just one disease but many diseases. Cancer begins in your cells, which are the building blocks of your body. Usually, your body forms new cells as needed, replacing old cells that die. Sometimes this process goes wrong. New cells grow even when you don't need them, and old cells don't die when they should.
The full article covers:
- What is cancer?
- What are the types of cancer?
- How does cancer develop?
- What are the symptoms of cancer?
- How is cancer diagnosed?
- What are the treatments for cancer?
- Can cancer be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert C7A.1 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C7A.1Overview
What is the ICD-10 code for malignant poorly differentiated neuroendocrine tumors?
The ICD-10-CM code for malignant poorly differentiated neuroendocrine tumors is C7A.1 (sometimes written as C7A1). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is C7A.1 (Malignant neuroendocrine tumors) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report malignant poorly differentiated neuroendocrine tumors on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does C7A.1 group to?
When malignant poorly differentiated neuroendocrine tumors is the principal diagnosis on an inpatient stay, it groups to MS-DRG 844, 827, 829, 843, 828, 826, 830, 845, with relative weights from 0.8443 to 4.7560 depending on complications. Higher weights mean higher Medicare reimbursement.
Is C7A.1 a CC or MCC?
CMS lists C7A.1 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 38 closely related codes in its exclusion list.
Does C7A.1 need an additional code?
When the condition applies, yes. The Use Additional Code note at C7A, which applies to C7A.1, reads: code to identify any associated endocrine syndrome, such as: carcinoid syndrome (E34.00). The additional code is reported after C7A.1.
What HCC is C7A.1?
C7A.1 (malignant poorly differentiated neuroendocrine tumors) maps to CMS-HCC Category 21 (Lymphoma and Other Cancers), commonly written as HCC 21, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 12 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 22.
Does C7A.1 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C7A.1 adds a risk adjustment factor of about 0.671 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.493 to 0.739 depending on the payment segment). A more severe related category (HCC 17, HCC 18, HCC 19, and HCC 20) supersedes it when both are reported. See the full factor table on the HCC 21 category page.
