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C7A.091 ICD-10-CM Code: Malignant carcinoid tumor of the thymus

C7A.091 maps to CMS-HCC V28 21. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools

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Code lookupC7A.091

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neuroendocrine tumors (C7A)

C7A.091

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Malignant carcinoid tumor of the thymus

A rare cancer that develops from hormone-producing cells in the thymus gland, located in the chest behind the breastbone.

Buddy the Bee presenting code insight

Buddy Insight

Malignant carcinoid tumor of the thymus is an extremely rare neuroendocrine malignancy arising from the thymus gland in the anterior mediastinum.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 21

Coefficient HCC 21: 0.671 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 012

Code-level coefficient reference

ESRD/PACE

HCC 12

Code-level coefficient reference

RXHCC

HCC 22

Code-level coefficient reference

Code Book Path

Official
C7A.0Malignant carcinoid tumorsC7A.09Malignant carcinoid tumors of other sitesC7A.091Malignant carcinoid tumor of the thymus

Inclusion Terms

Official

No inclusion terms are included in this display for C7A.091. Check the code and parent instructions in the Code Book.

Excludes 2

Official
  • malignant pancreatic islet cell tumors (C25.4)Inherited from C7A
  • Merkel cell carcinoma (C4A.-)Inherited from C7A

Related Codes

Official
C7A.090Malignant carcinoid tumor of the bronchus and lungC7A.092Malignant carcinoid tumor of the stomachC7A.093Malignant carcinoid tumor of the kidneyC7A.094Malignant carcinoid tumor of the foregut, unspecifiedC7A.095Malignant carcinoid tumor of the midgut, unspecified

Includes

Official

No Includes notes are included in this display for C7A.091. Check the code and parent instructions in the Code Book.

Excludes 1

Official

No Excludes 1 notes are included in this display for C7A.091. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for C7A.091. Check the code and parent instructions in the Code Book.

Use Additional

Official
  • code to identify any associated endocrine syndrome, such as:Inherited from C7A
  • carcinoid syndrome (E34.00)Inherited from C7A

Code Also

Official
  • any associated multiple endocrine neoplasia [MEN] syndromes (E31.2-)Inherited from C7A

Buddy Documentation Tip

HCC Buddy guidance
Pathology report confirming neuroendocrine/carcinoid histology of the thymus
Distinction from thymoma, thymic carcinoma, or other anterior mediastinal tumors
Documentation of any associated MEN1 syndrome or other endocrine neoplasia syndromes
Tumor stage and grade

MEAT Support

HCC Buddy guidance
Pathology report confirming neuroendocrine/carcinoid histology of the thymus
Distinction from thymoma, thymic carcinoma, or other anterior mediastinal tumors
Documentation of any associated MEN1 syndrome or other endocrine neoplasia syndromes
Tumor stage and grade

Audit Caution

HCC Buddy guidance
Confusing thymic carcinoid with thymoma — these are histologically distinct tumors with different ICD-10 codes
Failing to screen for and code associated MEN1 syndrome (E31.21) when present
Not coding ectopic ACTH production (Cushing syndrome E24.3) if documented as a manifestation
Using generic neuroendocrine tumor codes when the thymic site is specified

Common Mistakes

HCC Buddy guidance
C37 — Malignant neoplasm of thymus: Use C37 for thymoma or thymic carcinoma (non-neuroendocrine); C7A.091 is specifically for carcinoid/neuroendocrine histology
C7A.090 — Malignant carcinoid tumor of the bronchus and lung: Anatomically adjacent but distinct; verify whether the tumor originates in the thymus versus the lung/bronchus
D3A.091 — Benign carcinoid tumor of the thymus: Use D3A.091 only if the tumor demonstrates benign behavior

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is C7A.091 an HCC code?

Yes. C7A.091 (Malignant carcinoid tumor of the thymus) maps to HCC 21, Lymphoma and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.671. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: C7A.091 is billable and maps to V28 HCC 21, Lymphoma and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
C7A.091
Description
Malignant carcinoid tumor of the thymus
HCC (V28)
HCC 21 — Lymphoma and Other Cancers
RAF reference coefficient
0.671
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 21, Lymphoma and Other Cancers
0.671
ESRDHCC 12, Breast/Prostate/and Other Cancers and Tumors
Not separately weighted
RxHCCHCC 22, Prostate, Breast, Bladder, and Other Cancers and Tumors
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work C7A.091 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C7A.091

For C7A.091, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
  • EEvaluate: test results, medication response, or physical findings reviewed by the provider
  • AAssess: explicit mention in the assessment or plan with acknowledgment of status
  • TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Coder workflow notes

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What This Code Means

C7A.091 is the ICD-10-CM diagnosis code for malignant carcinoid tumor of the thymus. A rare cancer that develops from hormone-producing cells in the thymus gland, located in the chest behind the breastbone. C7A.091 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neuroendocrine tumors (c7a).

Under the CMS-HCC V28 risk adjustment model, C7A.091 maps to Lymphoma and Other Cancers (HCC 21) with a source-labeled community, non-dual, aged reference coefficient of 0.671. No V24 mapping is shown for C7A.091; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Thymic carcinoid tumors are uncommon; ensure documentation distinguishes this from thymoma or other thymic malignancies. For C7A.091, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for C7A.091 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Thymic carcinoid tumors are uncommon; ensure documentation distinguishes this from thymoma or other thymic malignancies
  • •Consider associated conditions like MEN syndromes, which may require additional coding

Clinical Significance

Malignant carcinoid tumor of the thymus is an extremely rare neuroendocrine malignancy arising from the thymus gland in the anterior mediastinum. Thymic carcinoids are more aggressive than typical carcinoid tumors and have a higher rate of local invasion and metastasis. They are frequently associated with Multiple Endocrine Neoplasia type 1 (MEN1) syndrome, requiring screening for associated endocrine tumors.

Documentation Requirements

  • ✓Pathology report confirming neuroendocrine/carcinoid histology of the thymus
  • ✓Distinction from thymoma, thymic carcinoma, or other anterior mediastinal tumors
  • ✓Documentation of any associated MEN1 syndrome or other endocrine neoplasia syndromes
  • ✓Tumor stage and grade
  • ✓Treatment plan (surgical resection, chemotherapy, radiation)
  • ✓Presence or absence of ectopic hormone production (Cushing syndrome from ACTH secretion)

Commonly Confused Codes

  • •C37: Malignant neoplasm of thymus: Use C37 for thymoma or thymic carcinoma (non-neuroendocrine); C7A.091 is specifically for carcinoid/neuroendocrine histology
  • •C7A.090: Malignant carcinoid tumor of the bronchus and lung: Anatomically adjacent but distinct; verify whether the tumor originates in the thymus versus the lung/bronchus
  • •D3A.091: Benign carcinoid tumor of the thymus: Use D3A.091 only if the tumor demonstrates benign behavior

Child Codes

C7A.090Malignant carcinoid tumor of the bronchus and lung
HCC 21
C7A.091Malignant carcinoid tumor of the thymus
HCC 21
C7A.092Malignant carcinoid tumor of the stomach
HCC 21
C7A.093Malignant carcinoid tumor of the kidney
HCC 21
C7A.094Malignant carcinoid tumor of the foregut, unspecified
HCC 21
C7A.095Malignant carcinoid tumor of the midgut, unspecified
HCC 21
C7A.096Malignant carcinoid tumor of the hindgut, unspecified
HCC 21
C7A.098Malignant carcinoid tumors of other sites
HCC 21

Code Hierarchy

└C7AMalignant neuroendocrine tumors└C7A.0Malignant carcinoid tumors└C7A.09Malignant carcinoid tumors of other sites└C7A.091Malignant carcinoid tumor of the thymus
└C7A.091Malignant carcinoid tumor of the thymus

Also searched as

  • C7A 091
  • C7A091

For C7A.091, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

C7A.091 maps to CMS-HCC V28 category 21, Lymphoma and Other Cancers. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C7A.091. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

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