Crystal's MCW Coder HubCPT Code 42845 — Radical Resection of Tonsil, Tonsillar Pillars, and/or Retromolar Trigone; Closure with Other Flap
Quick Reference
wRVU: 20.55 · Global: 090 · Assistant: ✅ Payable · Bilateral: ❌ N/A · Co-Surgeon (62): ✅ Commonly Applicable
📋 Full Code Descriptor
42845 — Radical resection of tonsil, tonsillar pillars, and/or retromolar trigone; closure with other flap
This code represents the most complex tier of the three-code radical oropharyngeal resection family. The ablative component is identical to its siblings — en bloc removal of the palatine tonsil and potentially the anterior (palatoglossal) and/or posterior (palatopharyngeal) tonsillar pillars and/or the retromolar trigone (the triangular mucosal area overlying the ascending mandibular ramus posterior to the last lower molar). What distinguishes 42845 is the reconstructive method: the surgical defect requires closure with an “other flap” — meaning a regional pedicled flap or free tissue transfer (microvascular free flap), rather than a simple local tissue rearrangement.
The phrase “other flap” in the descriptor is deliberate and encompasses a broad spectrum of reconstructive options:
- Regional/pedicled flaps — tissue harvested from a nearby but not immediately adjacent donor site, supplied by a named axial vessel pedicle that remains intact (e.g., pectoralis major myocutaneous flap, deltopectoral fasciocutaneous flap, temporalis muscle flap)
- Free tissue transfer (microvascular flap) — tissue completely harvested from a distant donor site and revascularized via microsurgical anastomosis to recipient vessels in the neck (e.g., radial forearm free flap, anterolateral thigh flap, fibula osteocutaneous flap)
The use of an “other flap” implies the defect is too large, too deep, or too geometrically complex to be closed with adjacent mucosal tissue alone. This typically correlates with advanced-stage disease (T3/T4), post-radiation tissue beds, or cases requiring simultaneous bony reconstruction.
🏗️ Anatomical & Surgical Context
| Structure | Description |
|---|---|
| Tonsil (palatine) | Lymphoid tissue within the tonsillar fossa; bounded anteriorly and posteriorly by the tonsillar pillars |
| Anterior tonsillar pillar | Palatoglossal arch; if resected, significant oropharyngeal competence disruption |
| Posterior tonsillar pillar | Palatopharyngeal arch; resection affects pharyngeal constrictor continuity |
| Retromolar trigone | Triangular mucosa overlying the coronoid process of the mandible; high-risk for SCC extension to adjacent structures |
| Pectoralis major flap | Most common regional pedicled option; based on thoracoacromial pedicle; provides bulk and skin paddle |
| Deltopectoral flap | Fasciocutaneous; medially based on perforators of the internal mammary; thin, pliable |
| Radial forearm free flap (RFFF) | Thin, pliable fasciocutaneous flap; gold standard for intraoral soft tissue reconstruction |
| Anterolateral thigh (ALT) free flap | Larger volume; based on lateral circumflex femoral system; used for larger defects |
| Fibula osteocutaneous free flap | When mandibular bony reconstruction is simultaneously needed |
| Temporalis muscle flap | Regional rotational flap; used for palate and lateral pharyngeal wall defects |
💰 Valuation & Reimbursement
| Field | Value |
|---|---|
| wRVU | 20.55 ^[CMS Physician Fee Schedule Final Rule 2025] |
| Global Period | 090 days |
| Assistant Surgeon Payable | ✅ Yes — Modifier 80, 82, or AS applicable |
| Co-Surgeon (Modifier 62) | ✅ Commonly applicable — ablative and reconstructive surgeons often co-operate |
| Bilateral Procedure | ❌ Not applicable by nature |
| Team Surgery (Modifier 66) | May apply in complex microvascular cases |
wRVU Comparison Within Code Family
The progressive increase in wRVU reflects the substantially greater operative work, technical complexity, and time involved in pedicled or microvascular reconstruction versus local tissue rearrangement.
Modifier -22 Consideration
Cases involving free tissue transfer with microsurgical anastomosis to a difficult or previously irradiated vessel, combined mandibulectomy, or extended resection into the base of tongue or soft palate may justify Modifier -22 (Increased Procedural Services) with supporting documentation of increased physician work and time.
🌲 Code Tree / Code Family
42842 — Radical resection of tonsil, tonsillar pillars, and/or retromolar trigone; WITHOUT closure
└── Defect left to granulate or intentionally left open
42844 — ...closure with LOCAL FLAP (e.g., tongue, buccal)
└── Adjacent intraoral tissue rotated or advanced
42845 — ...closure with OTHER FLAP ← THIS CODE
├── Regional pedicled flap (pectoralis major, deltopectoral, temporalis)
└── Free tissue transfer / microvascular free flap (RFFF, ALT, fibula)
Related codes in the same subsection:
| Code | Descriptor |
|---|---|
| 42800 | Biopsy; oropharynx |
| 42808 | Excision or destruction of lesion of pharynx, any method |
| 42820 | Tonsillectomy and adenoidectomy; younger than age 12 |
| 42821 | Tonsillectomy and adenoidectomy; age 12 or over |
| 42842 | Radical resection — without closure |
| 42844 | Radical resection — closure with local flap |
| 42845 | Radical resection — closure with other flap |
Reconstructive codes potentially used in conjunction:
| Code | Descriptor | Notes |
|---|---|---|
| 15756 | Free muscle or myocutaneous flap with microvascular anastomosis | Separately reportable when free flap is distinct from 42845 |
| 15757 | Free skin flap with microvascular anastomosis | Separately reportable — see Critical Coding Note below |
| 15758 | Free fascial flap with microvascular anastomosis | Separately reportable |
| 15732 | Muscle, myocutaneous, or fasciocutaneous flap; head and neck (e.g., temporalis, masseter) | Regional pedicled — potentially separately reportable |
| 15734 | Muscle, myocutaneous, or fasciocutaneous flap; trunk (e.g., pectoralis major) | Regional pedicled — potentially separately reportable |
| 35531 | Anastomosis, aortoceliac or aortomesenteric | Not applicable — see free flap codes above |
⚠️ Critical Coding Note: 42845 vs. Free Flap Codes
This Is One of the Most Complex Bundling Issues in Head & Neck Coding
The AMA and payer policies vary on whether the free tissue transfer component is bundled into 42845 or separately reportable using 15756, 15757, or 15758.
General guidance:
- 42845 describes the ablative procedure (radical resection) with an “other flap” closure — the descriptor’s intent centers on the resection.
- 15756–15758 describe the free flap harvest and microvascular anastomosis as standalone reconstructive procedures.
- In many cases, both codes may be reported when the resection surgeon and the reconstructive microsurgeon are the same physician, or when the extent of reconstructive work is documented separately.
- When Modifier -62 is used (co-surgeons), the ablative surgeon typically reports 42845--62 and the reconstructive surgeon reports the appropriate free flap code (15756–15758)--62, or vice versa depending on operative roles.
Always verify with your payer’s CCI (Correct Coding Initiative) edits before reporting 42845 alongside free flap codes. Some payers bundle the reconstruction into 42845; others permit separate reporting with appropriate modifiers.
✅ Includes (Bundled Into 42845)
The following are inherent components and are not separately reportable:
- Incision, exposure, and field preparation of the oropharynx
- Radical en bloc dissection and removal of tonsil ± tonsillar pillars ± retromolar trigone
- Intraoperative margin assessment (gross)
- Hemostasis throughout the ablative field
- Design, elevation, tunneling, and inset of the regional pedicled flap (if pedicled approach used)
- Routine closure of donor site (if primary closure is used at donor)
- Standard intraoperative monitoring (neuromonitoring, if used, may be separately reportable)
❌ Excludes / Separately Reportable
Report separately when documented and medically necessary
| Code | Descriptor | Notes |
|---|---|---|
| 15756 / 15757 / 15758 | Free muscle/skin/fascial flap with microvascular anastomosis | Potentially separately reportable — payer-dependent; see Critical Coding Note above |
| 15732 / 15734 | Pedicled muscle/myocutaneous flap (head/neck; trunk) | Separately reportable for regional pedicled flap work, payer-dependent |
| 31600 / 31601 | Tracheostomy, planned | Airway management — always separately reportable |
| 38700 / 38720 / 38724 | Cervical lymphadenectomy / radical / modified radical neck dissection | Distinct procedure; always separately reportable |
| 21045 | Radical resection of mandible | If segmental mandibulectomy required |
| 21025 | Excision of bone (mandible) | Marginal mandibulectomy |
| 21141–21196 | Reconstruction of midface/mandible | If bony reconstruction is concurrent |
| 64822 | Superficial radial sensory nerve transposition | If sensory reinnervation of flap performed |
| 69990 | Microsurgical techniques, requiring use of operating microscope | Separately reportable when microscope used for microvascular anastomosis — payer-specific |
| Anesthesia | Reported separately by anesthesia team |
🏥 MS-DRG Mapping
Inpatient Grouping
MS-DRG assignment for 42845 depends on principal diagnosis, CC/MCC status, and whether a tracheostomy was concurrently performed. Given the complexity of cases requiring regional or free flap reconstruction, tracheostomy is performed in the majority of inpatient 42845 cases — pushing these to the higher-weighted tracheostomy DRGs.
Without Concurrent Tracheostomy
| MS-DRG | Title | Trigger |
|---|---|---|
| 168 | Mouth Procedures with MCC | Malignancy + major complication/comorbidity |
| 169 | Mouth Procedures with CC | Malignancy + complication/comorbidity |
| 170 | Mouth Procedures without CC/MCC | Rare at this complexity level |
With Concurrent Tracheostomy (Most Common for 42845)
| MS-DRG | Title | Notes |
|---|---|---|
| 011 | Tracheostomy for Face, Mouth & Neck Diagnoses or Laryngectomy with MCC | Highest-weighted DRG in MDC 03; most common grouping for advanced oropharyngeal oncology |
| 012 | Tracheostomy for Face, Mouth & Neck Diagnoses or Laryngectomy with CC | |
| 013 | Tracheostomy for Face, Mouth & Neck Diagnoses or Laryngectomy without CC/MCC |
Inpatient Coder's Note
Cases involving 42845 are almost universally inpatient admissions requiring multi-day stays for flap monitoring, airway management, nutrition (NGT/PEG), and wound care. The following secondary diagnoses are critical to capture for accurate CC/MCC assignment and DRG optimization:
- Malnutrition (E43, E44.0, E44.1) — frequently present in head/neck oncology patients; MCC/CC depending on severity
- Dysphagia (R13.10–R13.19) — common preoperative and postoperative
- Prior radiation effects (Y84.2, T66.XXXA) — impacts flap selection and healing
- Postoperative complications (T81.30XA, T81.89XA) — if applicable
🔬 Commonly Associated ICD-10-CM Diagnoses
Primary Indications (Malignant)
| ICD-10-CM | Descriptor | HCC Mapping | Notes |
|---|---|---|---|
| C09.0 | Malignant neoplasm of tonsillar fossa | HCC 10 (v24) / HCC 17 (v28) | Most common primary site; fossa-specific |
| C09.1 | Malignant neoplasm of tonsillar pillar (anterior/posterior) | HCC 10 (v24) / HCC 17 (v28) | Pillar resection driving larger defect |
| C09.9 | Malignant neoplasm of tonsil, unspecified | HCC 10 (v24) / HCC 17 (v28) | When subsite not specified in documentation |
| C09.80 | Malignant neoplasm of overlapping sites of tonsil | HCC 10 (v24) / HCC 17 (v28) | Multi-subsite involvement — common at this complexity |
| C06.2 | Malignant neoplasm of retromolar area | HCC 10 (v24) / HCC 17 (v28) | Principal Dx when retromolar trigone is primary |
| C10.0 | Malignant neoplasm of vallecula | HCC 10 (v24) / HCC 17 (v28) | Extension toward base of tongue |
| C10.2 | Malignant neoplasm of lateral wall of oropharynx | HCC 10 (v24) / HCC 17 (v28) | Lateral oropharyngeal extension |
| C10.8 | Malignant neoplasm of overlapping sites of oropharynx | HCC 10 (v24) / HCC 17 (v28) | Advanced lesions crossing subsites — typical at 42845 complexity |
| C10.9 | Malignant neoplasm of oropharynx, unspecified | HCC 10 (v24) / HCC 17 (v28) | Use when subsite not documented |
| C41.1 | Malignant neoplasm of mandible | HCC 10 (v24) / HCC 17 (v28) | If mandibular bone involvement drives concurrent mandibulectomy |
Secondary / Staging / Comorbidity Codes
| ICD-10-CM | Descriptor | HCC | Notes |
|---|---|---|---|
| C77.0 | Secondary malignant neoplasm of lymph nodes of head, face, and neck | HCC 10 (v24) / HCC 8 (v28) | Nodal metastasis — MCC; drives neck dissection and tracheostomy |
| Z85.819 | Personal history of malignant neoplasm of lip, oral cavity, pharynx | Non-HCC | Recurrent disease context |
| E43 | Unspecified severe protein-calorie malnutrition | HCC 21 (v24) | MCC; extremely common in head/neck oncology patients |
| E44.0 | Moderate protein-calorie malnutrition | HCC 21 (v24) | CC; document nutritional status preoperatively |
| R13.10 | Dysphagia, unspecified | Non-HCC | CC in many groupers; document specifically |
| R13.19 | Other dysphagia | Non-HCC | Pharyngeal dysphagia more specific |
| J69.0 | Pneumonitis due to inhalation of food and vomit | HCC 114 (v24) | Aspiration — major postop risk and MCC |
| E11.65 | Type 2 diabetes mellitus with hyperglycemia | HCC 37 (v24) | MCC; complicates flap perfusion and wound healing |
| I50.9 | Heart failure, unspecified | HCC 85 (v24) | MCC; impacts surgical candidacy and recovery |
| B20 | Human immunodeficiency virus (HIV) disease | HCC 1 (v24) | MCC; immunocompromised state — affects oncologic outcomes |
| F17.210 | Nicotine dependence, cigarettes, uncomplicated | Non-HCC | Tobacco use — significant for wound healing; document for risk stratification |
| Z79.01 | Long-term use of anticoagulants | Non-HCC | CC potential; impacts hemostasis in microvascular field |
HCC Note
All oropharyngeal and oral cavity malignancies (C09.x, C10.x, C06.2, C41.1) map to cancer HCC categories under both CMS-HCC v24 and v28, carrying high RAF score weight. For Medicare Advantage patients, capture these diagnoses at every qualifying encounter — not only the surgical encounter — for longitudinal RAF scoring. Nodal metastasis (C77.0) maps to a separate, higher-weighted HCC for secondary malignancy. ^[CMS HCC Model v24/v28 Crosswalk, CMS.gov] ^[ICD-10-CM Official Guidelines for Coding and Reporting, FY2025]
🔧 Applicable Modifiers
| Modifier | Name | When to Use with 42845 |
|---|---|---|
| -22 | Increased Procedural Services | Extensive disease, difficult recipient vessels (post-radiation), combined mandibulectomy, prolonged operative time >8 hrs; requires documentation of increased work |
| -51 | Multiple Procedures | When 42845 is performed with other distinct procedures (neck dissection, tracheostomy) at the same operative session |
| -52 | Reduced Services | Planned flap not used due to intraoperative findings — document change in plan |
| -59 | Distinct Procedural Service | Separate anatomic site or distinct procedure; use when there is risk of inappropriate bundling |
| -62 | Two Surgeons | Commonly used — ablative ENT/H&N surgeon and reconstructive plastic/microsurgery surgeon co-operate as primary surgeons; each independently reports 42845-62 with supporting documentation of their individual contributions |
| -66 | Surgical Team | Complex free flap cases with multiple surgeons performing distinct simultaneous roles (e.g., simultaneous ablation and flap harvest); requires documentation |
| -80 | Assistant Surgeon | Physician assistant at surgery |
| -82 | Assistant Surgeon (qualified resident unavailable) | Teaching hospital context |
| -AS | Assistant at Surgery (PA, NP, CNS) | Mid-level practitioner assisting; payer-specific |
Modifier -62 Deep Dive
In head and neck oncology, the Modifier -62 (two surgeons) scenario is extremely common with 42845. A typical split:
- Ablative surgeon (ENT/Head & Neck): Performs the radical resection, neck dissection, prepares the recipient site and vessels → reports 42845--62 + 38724--51 (or appropriate neck dissection code)
- Reconstructive surgeon (Plastics/Microvascular): Harvests the free flap, performs microvascular anastomosis, inserts and insets the flap → reports 15757--62 (or applicable free flap code)
Both surgeons must document their distinct, non-overlapping roles in their individual operative notes. The combined reimbursement is split at 62.5% each (125% total split between two surgeons per CMS).
📖 Operative Note Key Elements (Documentation Requirements)
For accurate code assignment, audit defense, and appropriate modifier use, the operative note(s) must clearly document:
- Diagnosis driving the procedure — histology, T/N/M staging, specific subsite of origin
- Extent of ablative resection — tonsil alone vs. pillar involvement vs. retromolar trigone; depth of resection (mucosa only vs. musculature vs. periosteum/bone)
- Reason a local flap was insufficient — size of defect, depth, location, post-radiation tissue quality
- Specific flap used — named flap (e.g., “left radial forearm free flap,” “right pectoralis major myocutaneous pedicled flap”) — this is what distinguishes 42845 from 42844
- Flap dimensions — skin paddle size, pedicle length, vessel caliber
- Microsurgical anastomosis details (if free flap) — recipient vessels used, anastomosis technique (end-to-end vs. end-to-side), ischemia time
- Concurrent procedures — tracheostomy, neck dissection, mandibulectomy — each with independent documentation
- Surgeon roles — if co-surgeons, each operative report must specify which portions each surgeon performed
🧪 Coding Examples
Example 1 — T3 Tonsil SCC, Pectoralis Major Pedicled Flap, Neck Dissection, Tracheostomy
A 68-year-old male with T3N1M0 squamous cell carcinoma of the right tonsil with extension to the posterior tonsillar pillar undergoes radical resection of the right tonsil and posterior pillar. The defect is reconstructed with a right pectoralis major myocutaneous pedicled flap. Concurrent modified radical neck dissection (levels I–IV, right) and planned tracheostomy are performed.
CPT Codes:
- 42845-62 — Radical resection; closure with other flap (pectoralis major) (ablative surgeon)
- 15734-62 — Muscle, myocutaneous, or fasciocutaneous flap; trunk (reconstructive surgeon — payer-dependent; some bundle into 42845)
- 38724-51 — Cervical lymphadenectomy, modified radical neck dissection
- 31600 — Tracheostomy, planned
ICD-10-CM Codes:
- C09.1 — Malignant neoplasm of tonsillar pillar (principal diagnosis)
- C77.0 — Secondary malignant neoplasm of lymph nodes of head, face, and neck
- E44.0 — Moderate protein-calorie malnutrition
Expected MS-DRG:
- MS-DRG 011 — Tracheostomy for Face, Mouth & Neck Diagnoses with MCC (C77.0 = MCC)
Example 2 — Retromolar Trigone SCC, Radial Forearm Free Flap, Concurrent Marginal Mandibulectomy
A 54-year-old female with T2N0 squamous cell carcinoma of the left retromolar trigone with periosteal involvement of the mandible. Radical resection of the left retromolar trigone and anterior tonsillar pillar performed with marginal mandibulectomy. Defect reconstructed with left radial forearm free flap with microvascular anastomosis to the facial artery and internal jugular vein. Planned tracheostomy for airway protection.
CPT Codes:
- 42845 — Radical resection; closure with other flap (radial forearm free flap)
- 15757 — Free skin flap with microvascular anastomosis (separately reportable per payer CCI edits — verify)
- 21025 — Excision of bone (mandible); marginal mandibulectomy
- 31600 — Tracheostomy, planned
ICD-10-CM Codes:
- C06.2 — Malignant neoplasm of retromolar area (principal diagnosis)
- C41.1 — Malignant neoplasm of mandible (periosteal/bony involvement)
- R13.10 — Dysphagia, unspecified
Expected MS-DRG:
- MS-DRG 011 — Tracheostomy for Face, Mouth & Neck Diagnoses with MCC (C41.1 as MCC driver — verify CMS MCC list)
Example 3 — Recurrent Oropharyngeal Carcinoma, Post-Radiation, ALT Free Flap
A 61-year-old male with recurrent T4 squamous cell carcinoma of the oropharynx (overlapping sites) following prior chemoradiation presents for salvage resection. Radical resection of the right tonsil, both pillars, and retromolar trigone performed. Given the irradiated, fibrotic tissue bed and large defect, an anterolateral thigh (ALT) free flap is harvested and anastomosed to the superior thyroid artery and internal jugular vein. Simultaneous right comprehensive neck dissection (levels I–V) and tracheostomy performed.
CPT Codes:
- 42845-62 — Radical resection; closure with other flap (ALT free flap) (ablative surgeon)
- 15757-62 — Free skin flap with microvascular anastomosis (reconstructive surgeon — payer-dependent)
- 38720-51 — Cervical lymphadenectomy, complete (radical neck dissection)
- 31600 — Tracheostomy, planned
ICD-10-CM Codes:
- C10.8 — Malignant neoplasm of overlapping sites of oropharynx (principal)
- C77.0 — Secondary malignant neoplasm of lymph nodes of head, face, and neck
- E43 — Unspecified severe protein-calorie malnutrition
- Z85.819 — Personal history of malignant neoplasm of oral cavity and pharynx (recurrent disease context)
Expected MS-DRG:
- MS-DRG 011 — Tracheostomy for Face, Mouth & Neck Diagnoses with MCC (C77.0 + E43 = multiple MCCs; highest weighted DRG in MDC 03)
Example 4 — Temporal Muscle Flap, No Tracheostomy, No CC/MCC
A 47-year-old female with small T2N0 squamous cell carcinoma of the right tonsillar pillar. Radical resection performed; defect reconstructed with a temporalis muscle transposition flap. No neck dissection. No tracheostomy. No significant comorbidities. Healthy nonsmoker. Uneventful postoperative course.
CPT: 42845 ICD-10-CM: C09.1 — Malignant neoplasm of tonsillar pillar Expected MS-DRG: 170 — Mouth Procedures without CC/MCC
Query Opportunity
This scenario should prompt a coder to query the physician for documentation of nutritional status, tobacco/alcohol use history, and any preoperative comorbidities. A single CC can shift the DRG from 170 to 169, and a single MCC shifts it to 168, with significant reimbursement impact. Always assess for undercoded comorbidities in oncology patients.
⚠️ Coding Pitfalls & Compliance Notes
Common Errors
- Coding 42844 instead of 42845: If the operative report documents a pectoralis major flap, radial forearm free flap, ALT flap, or any regional pedicled flap, the correct code is 42845. A tongue flap or buccal mucosal flap is 42844. The flap type must be explicitly documented — query the surgeon if not specified.
- Failing to separately report neck dissection: Neck dissection is never bundled into 42845. It is always separately reportable.
- Missing tracheostomy code: 31600 or 31601 should always be independently reported when a tracheostomy is performed. This is the most impactful code for MS-DRG assignment in these cases (shifts to MS-DRG 011–013).
- Overlooking Modifier -62 eligibility: When two surgeons perform distinct operative roles, both should report the applicable procedure codes with Modifier -62 and individual operative reports. Failure to use -62 when applicable leads to payment denials or inaccurate attribution.
- Free flap coding ambiguity: Whether 15756–15758 can be separately reported alongside 42845 is payer-dependent. Always check CCI edits. Do not assume bundling or separation without verification.
- HCC capture failure: Oropharyngeal malignancies (C09.x, C10.x, C06.2) and nodal metastasis (C77.0) carry significant HCC weight. For Medicare Advantage patients, ensure these are coded at every qualifying encounter for complete RAF scoring.
- Undercoding malnutrition and dysphagia: These diagnoses are nearly universal in head and neck cancer patients requiring radical oropharyngeal surgery. Capture them as additional diagnoses when clinically documented — they are frequent CC/MCC drivers.
🔗 Related Notes
- 42842 — Radical resection without closure
- 42844 — Radical resection with local flap
- 15756 — Free muscle or myocutaneous flap with microvascular anastomosis
- 15757 — Free skin flap with microvascular anastomosis
- 15758 — Free fascial flap with microvascular anastomosis
- 15732 — Pedicled muscle flap; head and neck
- 15734 — Pedicled muscle flap; trunk
- 38720 — Cervical lymphadenectomy, complete (radical neck dissection)
- 38724 — Cervical lymphadenectomy, modified radical neck dissection
- 31600 — Tracheostomy, planned
- 21045 — Radical resection of mandible
- 21025 — Excision of bone (mandible)
- C09.0 — Malignant neoplasm of tonsillar fossa
- C09.1 — Malignant neoplasm of tonsillar pillar
- C06.2 — Malignant neoplasm of retromolar area
- C10.8 — Malignant neoplasm of overlapping sites of oropharynx
AMA CPT Codebook 2025 · CMS Physician Fee Schedule Final Rule 2025 · CMS MS-DRG ICD-10 Version 42 Definitions Manual · CMS-HCC Risk Adjustment Model v24/v28 · ICD-10-CM Official Guidelines for Coding and Reporting FY2025 · CMS National Correct Coding Initiative (NCCI) Policy Manual · AAPC CPC/CIC Coding Reference