Cigna modified MM 0561 for thymus tissue transplantation, effective September 26, 2025. Here's what billing teams need to know before claims go out.
Cigna Healthcare updated its coverage policy for thymus tissue transplantation — also known as cultured thymus tissue (CTT) or Rethymic® (allogenic processed thymus tissue-agdc). The revision to MM 0561 in the Cigna system affects claims billed under CPT codes 27599 and 60699, as well as HCPCS codes C9399, J3490, and J3590. If your practice or facility performs this procedure for pediatric patients with complete DiGeorge syndrome or related congenital endocrine gland anomalies, this coverage policy change affects your reimbursement.
Quick-Reference Table
| Field | Detail |
|---|---|
| Payer | Cigna Healthcare |
| Policy | Thymus Tissue Transplantation |
| Policy Code | MM 0561 |
| Change Type | Modified |
| Effective Date | September 26, 2025 |
| Impact Level | High |
| Specialties Affected | Pediatric immunology, pediatric surgery, endocrine surgery, transplant programs, specialty pharmacy |
| Key Action | Update charge capture to include ICD-10 D82.1 or Q89.2 and verify prior authorization before billing 60699 or J3590 for Rethymic® |
Cigna Thymus Tissue Transplantation Coverage Criteria and Medical Necessity Requirements 2025
Cigna covers thymus tissue transplantation as medically necessary when specific clinical criteria are met. The coverage position under MM 0561 applies to CTT — including the FDA-approved product Rethymic® — billed as an unlisted endocrine procedure or an unclassified biologic.
The two primary diagnoses that drive coverage are D82.1 (DiGeorge's syndrome) and Q89.2 (congenital malformations of other endocrine glands). Your claims need one of these ICD-10 codes attached. A claim for 60699 or J3590 without one of these diagnosis codes will almost certainly result in a claim denial.
Medical necessity documentation must support the diagnosis. That means the medical record should reflect the clinical picture — confirmed thymic aplasia or hypoplasia, immune deficiency consistent with DiGeorge syndrome, and the treating physician's rationale for transplantation over alternative immunologic management.
Prior authorization is a near-certainty for this procedure. Cigna's coverage policy for high-cost biologics and complex surgical interventions consistently requires prior auth before the service date. Confirm prior authorization requirements with your Cigna provider representative before scheduling. If your compliance officer hasn't reviewed MM 0561 against your specific plan contracts, loop them in now — plan-level exclusions can override the coverage policy even when criteria are met.
Rethymic® is a high-cost biologic product. Reimbursement under J3590 (unclassified biologics) requires invoice-based pricing documentation in most cases. Get that documentation lined up before claims drop.
Cigna Thymus Tissue Transplantation Exclusions and Non-Covered Indications
The policy doesn't list exhaustive exclusions, but the unlisted and unclassified code structure tells you something important. When Cigna assigns coverage to unlisted CPT codes like 27599 and 60699, coverage is conditional — not automatic.
CPT 27599 is listed as an unlisted femur or knee procedure. Its presence in this policy is unusual on its face. The most likely explanation is that thigh-site implantation of thymus tissue uses this code when no more specific descriptor applies. Bill it wrong — without the matching diagnosis and supporting operative notes — and you're looking at a claim denial based on code-to-diagnosis mismatch.
Any indication not covered by D82.1 or Q89.2 falls outside this policy. If a patient has a secondary immune condition without a confirmed DiGeorge or congenital endocrine gland malformation diagnosis, that claim won't survive Cigna's medical necessity review under MM 0561.
Coverage Indications at a Glance
| Indication | Status | Relevant Codes | Notes |
|---|---|---|---|
| Complete DiGeorge syndrome (thymic aplasia) | Covered — medical necessity criteria must be met | CPT 60699, HCPCS J3590, C9399, ICD-10 D82.1 | Prior auth likely required; document immune deficiency thoroughly |
| Congenital malformation of other endocrine glands with thymic involvement | Covered — medical necessity criteria must be met | CPT 60699, HCPCS J3490, J3590, ICD-10 Q89.2 | Confirm Cigna plan-level coverage; specialty pharmacy coordination required for Rethymic® |
| Thigh/femoral site implantation procedure | Covered — when criteria are met | CPT 27599, ICD-10 D82.1 or Q89.2 | Use with matching diagnosis; attach operative notes to avoid denial |
| Immune deficiency without confirmed DiGeorge or congenital endocrine malformation | Not covered under this policy | — | Diagnosis must support D82.1 or Q89.2; off-label use not addressed |
Cigna Thymus Tissue Transplantation Billing Guidelines and Action Items 2025
The effective date of September 26, 2025 means these requirements are active now. Don't wait.
| # | Action Item |
|---|---|
| 1 | Update your charge capture to include ICD-10 D82.1 or Q89.2 on every claim for thymus tissue transplantation. These are the two diagnosis codes covered under MM 0561. A claim without them won't meet Cigna's medical necessity threshold. |
| 2 | Confirm prior authorization before the procedure date. Call your Cigna provider contact or check the authorization portal. Thymus tissue transplantation is a high-cost, low-volume procedure — Cigna will expect prior auth documentation on file before adjudication. |
| 3 | Document the invoice price for Rethymic® and attach it to claims billed under J3590. Unclassified biologic codes (J3590) require cost documentation for accurate reimbursement. Without it, Cigna can reimburse at a default rate that doesn't reflect actual acquisition cost. |
| 4 | Review how your team codes the implantation site. CPT 27599 (unlisted femur or knee procedure) appears alongside 60699 (unlisted endocrine procedure) in this policy. Make sure your coding team understands when each applies based on surgical approach and anatomy. If there's any ambiguity, query the surgeon before billing. |
| 5 | Audit any claims submitted on or after September 26, 2025 to confirm they reflect the updated billing guidelines. If you billed thymus tissue transplantation under Cigna before verifying the revised MM 0561 criteria, pull those claims and check the diagnosis codes, prior auth status, and HCPCS code selection. |
| 6 | Engage your compliance officer if you're billing J3490 (unclassified drugs) instead of J3590 (unclassified biologics) for Rethymic®. Rethymic® is a biologic product. J3590 is the appropriate code. Billing J3490 for a biologic creates a medical necessity and coding compliance issue. Correct your charge master if this is happening. |
| 7 | Coordinate with specialty pharmacy if your facility doesn't stock Rethymic® in-house. The product is FDA-approved and HCPCS-covered, but the buy-and-bill workflow for a high-cost biologic like this needs to be set up before the case, not after. |
| Previous Version | Current Version |
|---|---|
| Coverage is considered experimental and investigational for all indications | Coverage is considered medically necessary when specific criteria are met |
| Prior authorization is not required | Prior authorization is required for initial treatment |
| Documentation must include clinical history | Documentation must include clinical history |
| Re-review every 24 months | Re-review every 12 months with updated clinical documentation |
CPT, HCPCS, and ICD-10 Codes for Thymus Tissue Transplantation Under MM 0561
Covered CPT Codes (When Medical Necessity Criteria Are Met)
| Code | Type | Description |
|---|---|---|
| 27599 | CPT | Unlisted procedure, femur or knee |
| 60699 | CPT | Unlisted procedure, endocrine system |
Covered HCPCS Codes (When Medical Necessity Criteria Are Met)
| Code | Type | Description |
|---|---|---|
| C9399 | HCPCS | Unclassified drugs or biologicals |
| J3490 | HCPCS | Unclassified drugs |
| J3590 | HCPCS | Unclassified biologics |
Key ICD-10-CM Diagnosis Codes
| Code | Description |
|---|---|
| D82.1 | Di George's syndrome |
| Q89.2 | Congenital malformations of other endocrine glands |
A note on unlisted and unclassified codes: Every code in this policy is unlisted (CPT) or unclassified (HCPCS). That's not a quirk — it reflects where thymus tissue transplantation sits in the coding ecosystem. There's no dedicated CPT code for this procedure yet. That means your claims carry higher scrutiny by default. Cigna will want to see operative reports, diagnosis confirmation, and prior auth on file. Build that into your workflow now, not when a claim gets kicked back.
The combination of J3490 and J3590 on the same policy also raises a practical question for your coding team: which one applies to Rethymic® in your claims? Rethymic® is a biologic. J3590 is the correct code. J3490 is listed in the policy, but its inclusion likely covers scenarios where a drug component is separately billed. If you're not sure how to split these for your specific claim mix, ask your billing consultant before the effective date passes.
Get the Full Picture for CPT 27599
Track this policy across versions, search 1,500+ policies by CPT code, and get real-time alerts when any payer changes coverage.