15757

🔬 CPT Code 15757 — Free Skin Flap with Microvascular Anastomosis

Quick Reference

Global Period: 090 days | wRVU: 30.32 | Assistant Payable: ✅ Yes | Co-Surgeon: ✅ Yes | Category: Reconstructive – Integumentary

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📋 Official CPT Description

CPT 15757 — Free skin flap with microvascular anastomosis

This code describes the harvest and microsurgical transfer of a free skin flap — which in clinical practice most commonly refers to a fasciocutaneous flap (skin + subcutaneous tissue + investing fascia, without a muscle component) — from a donor site to a geographically distant recipient site, requiring microvascular anastomosis to restore perfusion to the transferred tissue at the new location.

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🧠 Detailed Clinical Description

What Is a Free Skin Flap?

A free skin flap under 15757 is a composite unit of tissue that includes:

• Skin (epidermis + dermis)
• Subcutaneous adipose tissue
• Deep investing fascia (in fasciocutaneous variants)
• Named perforating vessel(s) supplying the skin territory

It does not include a significant muscle component. This is the primary distinction separating 15757 from 15756 (muscle/myocutaneous) and 15758 (fascial/fasciocutaneous flap only, no skin paddle).

Free Flap Type Comparison

Code	Tissue Transferred	Skin Paddle?	Muscle?	Fascia?
15756	Muscle or myocutaneous	Optional	✅ Yes	Optional
15757	Skin / fasciocutaneous	✅ Yes	❌ No	✅ Often
15758	Fascial / fasciocutaneous	❌ No skin	❌ No	✅ Yes

ALT Flap Classification

The Anterolateral Thigh (ALT) flap, when harvested as a pure fasciocutaneous flap without incorporating the vastus lateralis muscle, is the quintessential 15757 case. It is one of the most commonly performed free flaps globally and drives the majority of 15757 volume in high-volume reconstructive centers.

Surgical Steps Included in 15757

1. Preoperative vascular assessment — Handheld Doppler, CT angiography, or duplex ultrasound to map perforating vessels (not separately billable within global)
2. Donor site dissection — Identification and isolation of the skin paddle on its perforating vessel(s) and vascular pedicle
3. Flap elevation — Subfascial or suprafascial dissection depending on flap design and recipient needs
4. Pedicle ligation and complete flap detachment — Vessel division, marking proximal/distal ends
5. Recipient site preparation — Debridement, tumor bed development, or wound bed conditioning
6. Microvascular anastomosis — Arterial and venous coaptation to recipient vessels under operative microscopy or high-magnification loupes (end-to-end or end-to-side)
7. Flap inset — Tailoring and securing the skin paddle into the recipient defect
8. Donor site closure — Primary closure or skin graft of donor site (skin graft billed separately if required; see Excludes)
9. Postoperative flap monitoring — Included in global period

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💰 Reimbursement & RVU Profile

Component	Value
Work RVU (wRVU)	30.32 CMS MPFS 2025
Global Period	090 days
Assistant Surgeon Payable	✅ Yes (Indicator: 1)
Co-Surgeon Payable	✅ Yes
Team Surgery	✅ Yes
Facility Only	Yes (hospital/ASC setting)
Multiple Procedure Indicator	2 (standard reduction applies)
Bilateral Surgery Indicator	0 (not applicable)

wRVU Differential vs. 15756

15757 carries a lower wRVU (30.32) compared to 15756 (35.38) reflecting the absence of muscle harvest, reduced donor site morbidity, and generally shorter operative time. However, the fasciocutaneous free flap remains among the highest-complexity codes in the fee schedule and microsurgical expertise is equally required.

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✅ Included Services (Bundled into 15757)

The following services are not separately reportable when performed as integral components of 15757:

• Harvest and elevation of the skin/fasciocutaneous flap from the donor site
• Microvascular arterial and venous anastomosis (primary)
• Flap inset and suture closure into recipient defect
• Simple or intermediate donor site closure
• Intraoperative Doppler or perfusion assessment of flap viability
• Routine wound irrigation and debridement at recipient site
• Standard postoperative monitoring within the 90-day global period
• Routine dressing changes and staple/suture removal within global period

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❌ Excludes / Separately Reportable Services

The following may be billed separately when clearly documented as distinct services:

Separate Service	Code
Nerve coaptation performed with the free flap	64905, 64907
Skin graft to close donor site (when primary closure not possible)	15100–15115
Complex donor site closure (meeting criteria for complex repair)	13100–13160
Re-exploration/revision of microvascular anastomosis (separate session)	15757 with modifier 78
Bone graft for composite reconstruction	20900–20902
Secondary debridement of unrelated wound	97597–97598
Vein graft interposition for pedicle extension	35500
Staged flap division or inset (subsequent session)	15630

NCCI Bundling

CMS NCCI edits bundle many wound preparation, closure, and debridement codes with 15757. Verify current NCCI column assignments before appending modifier -59 for any additional procedures. Append -59 only when the additional service is performed at a separate anatomical site with distinct documentation.

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🏥 Common Donor Flap Sources (Skin / Fasciocutaneous)

Donor Flap	Primary Tissue	Vascular Pedicle	Common Recipient Use
Anterolateral Thigh (ALT)	Skin + fascia ± muscle	Lateral circumflex femoral a/v (descending branch)	Oral cavity, pharynx, scalp, extremity, perineum
Radial Forearm (RFFF)	Thin skin + fascia	Radial artery / cephalic vein	Oral cavity, tongue, pharynx, hand/digit
Medial Sural Artery Perforator (MSAP)	Thin skin + fascia	Medial sural artery	Oral cavity, facial reconstruction
Deep Inferior Epigastric Perforator (DIEP)	Skin + fat (no muscle)	Deep inferior epigastric a/v	Breast reconstruction
Superior Gluteal Artery Perforator (SGAP)	Skin + fat	Superior gluteal a/v	Breast reconstruction
Thoracodorsal Artery Perforator (TDAP)	Skin + fascia (no lat)	Thoracodorsal a/v	Head/neck, extremity
Lateral Arm Flap	Skin + fascia	Posterior radial collateral a/v	Hand, face, oral cavity
Fibula Free Flap (soft tissue component)	Skin paddle only	Peroneal a/v perforators	Jaw reconstruction skin coverage

DIEP vs. TRAM / Free TRAM

The DIEP flap is a perforator flap harvested with skin and fat only — no rectus muscle is taken. It is properly coded as 15757 (free skin/fasciocutaneous flap) rather than 15756, since no functional muscle is included. In contrast, a free TRAM flap includes the rectus abdominis muscle and maps to 15756. Documentation of whether muscle was included is essential to code selection.

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🏷️ Applicable Modifiers

Modifier	Description	When to Use
-51	Multiple procedures	When 15757 is billed alongside another major procedure (e.g., tumor extirpation, jaw reconstruction)
-59	Distinct procedural service	To unbundle separately identifiable service at a distinct anatomical site
-80	Assistant surgeon	Second surgeon at the table; medically necessary and payable given microsurgical requirements
-82	Assistant surgeon (no resident available)	Teaching hospital alternative to -80
-AS	Assistant at surgery – NP/PA	Non-physician practitioner assisting
-22	Increased procedural complexity	Prior radiation, obesity, complex anatomy, significantly prolonged operative time; requires documentation
-52	Reduced services	Partial procedure; rarely applicable for free flap
-78	Return to OR for related procedure	Re-exploration for anastomotic thrombosis, hematoma, or partial flap loss during global period
-79	Unrelated procedure during global period	Separate, unrelated surgery within 90 days
-LT / -RT	Left / Right side	Laterality of recipient site when applicable

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🩺 ICD-10-CM Diagnoses Commonly Paired with 15757

Malignant Neoplasms (Oncologic Reconstruction)

ICD-10-CM	Description	HCC?
C02.9	Malignant neoplasm of tongue, unspecified	✅ HCC 11
C04.9	Malignant neoplasm of floor of mouth, unspecified	✅ HCC 11
C05.9	Malignant neoplasm of palate, unspecified	✅ HCC 11
C06.9	Malignant neoplasm of mouth, unspecified	✅ HCC 11
C09.9	Malignant neoplasm of tonsil, unspecified	✅ HCC 11
C10.9	Malignant neoplasm of oropharynx, unspecified	✅ HCC 11
C11.9	Malignant neoplasm of nasopharynx, unspecified	✅ HCC 11
C13.9	Malignant neoplasm of hypopharynx, unspecified	✅ HCC 11
C32.9	Malignant neoplasm of larynx, unspecified	✅ HCC 11
C41.0	Malignant neoplasm of bones of skull and face	✅ HCC 11
C44.319	Squamous cell carcinoma of skin, unspecified part of face	✅ HCC 12
C50.911	Malignant neoplasm of unspecified site of right female breast	✅ HCC 12
C50.912	Malignant neoplasm of unspecified site of left female breast	✅ HCC 12
C67.9	Malignant neoplasm of bladder, unspecified	✅ HCC 11

HCC Note — Active vs. History

When free flap reconstruction is performed as part of the ongoing cancer treatment episode, use the active neoplasm ICD-10-CM code (e.g., C02.9) — not the personal history code. Active malignancy codes carry HCC weight and impact risk adjustment scores for Medicare Advantage and value-based contracts. Switch to Z85.xx only after the patient is considered disease-free and treatment is complete.

Traumatic / Acute Wounds

ICD-10-CM	Description	HCC?
S01.90XA	Open wound of head, unspecified, initial encounter	❌
S11.90XA	Open wound of neck, unspecified, initial encounter	❌
S41.001A	Unspecified open wound of right shoulder, initial	❌
S51.801A	Unspecified open wound of right forearm, initial	❌
S61.401A	Unspecified open wound of right hand, initial	❌
S81.001A	Unspecified open wound of right knee, initial	❌
S81.801A	Unspecified open wound of right lower leg, initial	❌
T14.8XXA	Other injury of unspecified body region, initial	❌

Chronic Wounds / Non-Healing Ulcers

ICD-10-CM	Description	HCC?
L89.159	Pressure ulcer of sacral region, unspecified stage	❌
L89.319	Pressure ulcer of right buttock, unspecified stage	❌
L97.119	Non-pressure chronic ulcer of right thigh, unspecified severity	❌
L97.419	Non-pressure chronic ulcer of right heel and midfoot	❌
E11.621	Type 2 diabetes with foot ulcer	✅ HCC 18
E11.628	Type 2 diabetes with other skin complications	✅ HCC 18

Diabetic Wound Coding

When a diabetic patient undergoes free flap reconstruction for a chronic foot or lower extremity ulcer, code both the diabetes with complication (e.g., E11.621) and the ulcer site (e.g., L97.419) per ICD-10-CM guidelines. The diabetes code carries HCC 18 weight — capturing it correctly is critical in RAF-score environments.

Post-Mastectomy / Breast Reconstruction

ICD-10-CM	Description	HCC?
Z42.1	Encounter for breast reconstruction following mastectomy	❌
N65.1	Disproportion of reconstructed breast	❌
Z85.3	Personal history of malignant neoplasm of breast	❌
Z90.11	Acquired absence of right breast and nipple	❌
Z90.12	Acquired absence of left breast and nipple	❌
Z90.13	Acquired absence of bilateral breasts and nipples	❌

Osteomyelitis / Infection-Related

ICD-10-CM	Description	HCC?
M86.9	Osteomyelitis, unspecified	✅ HCC 39
M86.162	Other acute osteomyelitis, left tibia and fibula	✅ HCC 39
M86.672	Other chronic osteomyelitis, left ankle and foot	✅ HCC 39
L03.115	Cellulitis of right foot	❌

Status / Encounter Codes

ICD-10-CM	Description	HCC?
Z42.8	Encounter for other plastic/reconstructive surgery following healed injury or procedure	❌
Z87.39	Personal history of other musculoskeletal disorders	❌
Z85.819	Personal history of malignant neoplasm of unspecified site	❌

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🏨 MS-DRG Mapping

Inpatient Context

In the inpatient hospital setting, procedures are coded in ICD-10-PCS, not CPT. However, the complexity and nature of the underlying procedure drives MS-DRG assignment. Free fasciocutaneous flap reconstruction maps across several DRG families depending on the principal diagnosis and CC/MCC burden.

Head & Neck Oncologic Reconstruction

MS-DRG	Description	Approx. Relative Weight
168	Major Head & Neck Procedures w/ MCC	~3.8–4.2
169	Major Head & Neck Procedures w/ CC	~2.5–2.9
170	Major Head & Neck Procedures w/o CC/MCC	~1.8–2.1

Skin / Soft Tissue Reconstruction

MS-DRG	Description	Approx. Relative Weight
573	Skin Graft and/or Debridement w/ MCC	~3.7–4.5
574	Skin Graft and/or Debridement w/ CC	~2.2–2.6
575	Skin Graft and/or Debridement w/o CC/MCC	~1.5–1.8

Breast Reconstruction

MS-DRG	Description	Approx. Relative Weight
582	Mastectomy for Malignancy w/ CC/MCC	~1.9–2.3
583	Mastectomy for Malignancy w/o CC/MCC	~1.4–1.7

Lower Extremity

MS-DRG	Description	Approx. Relative Weight
485	Knee Procedures w/ PDX Infection w/ MCC	~3.5–4.0
492	Lower Extremity & Humerus Procedures w/ MCC	~3.0–3.5
493	Lower Extremity & Humerus Procedures w/ CC	~2.0–2.4

DRG Optimization

Accurately capturing all MCC-level diagnoses — sepsis, significant respiratory failure, severe malnutrition — elevates the case to the highest-weighted DRG tier. Query the treating surgeon when clinical indicators are documented but the diagnosis is not explicitly stated. For head/neck free flap cases, prior radiation-induced complications (e.g., osteoradionecrosis, fistula) may further support MCC-level comorbidity capture.

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🌳 CPT Code Tree — Free Flap Family

Free Flaps with Microvascular Anastomosis
├── 15756 — Free MUSCLE or MYOCUTANEOUS flap
│     └── Tissue: Muscle only OR Muscle + overlying skin
│
├── 15757 ← FREE SKIN / FASCIOCUTANEOUS FLAP (THIS CODE)
│     └── Tissue: Skin + subcutaneous fat ± investing fascia (NO muscle)
│
└── 15758 — Free FASCIAL / FASCIOCUTANEOUS flap
      └── Tissue: Fascia only — no skin paddle transferred

Related Pedicle / Local Flap Codes (not free flaps):
├── 15732 — Muscle/myocutaneous flap, head & neck (pedicle)
├── 15733 — Muscle/myocutaneous flap, upper extremity (pedicle)
├── 15740 — Island pedicle flap
└── 15750 — Neurovascular pedicle flap

Perforator / Nerve Considerations:
├── 64905 — Nerve pedicle transfer, first stage
└── 64907 — Nerve pedicle transfer, second stage

Donor Site Closure (if skin graft required):
├── 15100 — Split-thickness autograft, trunk/arms/legs, first 100 sq cm
└── 15115 — Split-thickness autograft, face/scalp/eyelids, first 100 sq cm

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🗂️ ICD-10-PCS Context (Inpatient Coding)

Inpatient Coder Note (CIC Relevance)

CPT codes are not assigned for inpatient hospital stays. The correct coding vehicle is ICD-10-PCS. A free skin/fasciocutaneous flap reconstruction — where the tissue is completely detached and revascularized — is typically coded under the Replacement root operation (putting in or on biological/synthetic material that physically takes the place and/or function of all or a portion of a body part).

General ICD-10-PCS axis logic — free fasciocutaneous flap:

Axis	Value
Section	0 – Medical & Surgical
Body System	H – Skin and Breast (or N – Head & Facial Bones region depending on recipient site)
Root Operation	R – Replacement
Body Part	Specific recipient site (e.g., Skin, Face; Skin, Scalp; Skin, Right Lower Leg)
Approach	0 – Open
Device	7 – Autologous Tissue Substitute
Qualifier	X – Diagnostic or Z – No Qualifier (site-dependent)

Two-Code Logic for Free Flaps in PCS

Assign separate ICD-10-PCS codes for:

1. The donor site — typically an Excision (root operation B) of skin/fascia from the donor location (e.g., thigh, forearm)
2. The recipient site — Replacement with autologous tissue at the defect site

Both the harvest and the anastomotic reconstruction represent distinct procedural steps coded independently in PCS.

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📝 Coding Examples

Example 1 — Oral Cavity Reconstruction (Otolaryngology / Head & Neck)

Clinical Scenario: Patient with T3 squamous cell carcinoma of the left lateral tongue undergoes hemiglossectomy with left selective neck dissection (levels I–IV). Intraoperative defect closure achieved with a radial forearm fasciocutaneous free flap anastomosed end-to-side to the facial artery and end-to-end to the internal jugular branch vein.

CPT Codes:

• 15757 — Free radial forearm fasciocutaneous flap with microvascular anastomosis
• 41155 — Glossectomy with laryngectomy (or appropriate partial glossectomy code with modifier -51)
• 38720 — Cervical lymphadenectomy (radical neck dissection) (with modifier -51)

ICD-10-CM:

• C02.2 — Malignant neoplasm of left lateral tongue (principal)
• Z79.01 — Long-term use of anticoagulants (if applicable)

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Example 2 — Breast Reconstruction (DIEP Flap)

Clinical Scenario: Patient with prior right mastectomy for breast cancer now presents for delayed autologous breast reconstruction. Plastic surgery performs a right DIEP (deep inferior epigastric perforator) flap: skin and fat harvested from the lower abdomen without muscle, microsurgically anastomosed to the right internal mammary artery and vein.

CPT Codes:

• 15757 — Free DIEP fasciocutaneous/skin flap with microvascular anastomosis
• (Contralateral symmetry procedure coded separately if performed — e.g., mastopexy 19316 with modifier -51)

ICD-10-CM:

• Z42.1 — Encounter for breast reconstruction following mastectomy (principal)
• Z90.11 — Acquired absence of right breast and nipple
• Z85.3 — Personal history of malignant neoplasm of breast

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Example 3 — Lower Extremity Trauma (Orthopedic / Plastic)

Clinical Scenario: Patient sustains a Gustilo type IIIB open fracture of the left tibia with exposed hardware and significant soft tissue loss. Orthopedics stabilizes with external fixation; plastic surgery performs an ALT (anterolateral thigh) fasciocutaneous free flap for soft tissue coverage, anastomosed to the anterior tibial vessels.

CPT Codes:

• 15757 — Free ALT fasciocutaneous flap with microvascular anastomosis
• 27759 — Treatment of tibial shaft fracture (with modifier -51)
• 15100 — Split-thickness autograft for donor site closure, if primary closure not possible (with modifier -59)

ICD-10-CM:

• S82.202A — Unspecified fracture of shaft of left tibia, initial encounter for open fracture type IIIA, IIIB, or IIIC
• S81.802A — Open wound of left lower leg, initial encounter
• T84.198A — Other mechanical complication of other bone devices, initial (if hardware present)

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Example 4 — Oropharyngeal Reconstruction with Sensate Flap (Otolaryngology)

Clinical Scenario: Patient with recurrent T2 carcinoma of the right tonsil and soft palate, post-radiation. Resection followed by reconstruction with a free medial sural artery perforator (MSAP) fasciocutaneous flap. Intraoperatively, the surgeon performs a nerve coaptation to the flap’s cutaneous nerve for sensory re-innervation.

CPT Codes:

• 15757 — Free MSAP fasciocutaneous flap with microvascular anastomosis
• 64905 — Nerve pedicle transfer, first stage (nerve anastomosis — separately reportable with modifier -59)
• Resection code with modifier -51

ICD-10-CM:

• C10.9 — Malignant neoplasm of oropharynx, unspecified
• Z85.819 — Personal history of malignant neoplasm (use only if prior cancer is resolved; use active code if still under treatment)

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Example 5 — Return to OR During Global Period

Clinical Scenario: Patient is POD #1 following free ALT flap for tongue reconstruction. Bedside Doppler signal lost; patient taken back emergently for re-exploration revealing venous thrombosis. Anastomosis taken down, thrombus evacuated, vein graft interposed, re-anastomosis performed.

CPT Codes:

• 15757 with modifier -78 — Return to OR for related procedure during postoperative period
• 35500 — Harvest of vein for bypass (if vein graft interposition documented separately — verify NCCI and append modifier -59)

ICD-10-CM:

• T87.9 — Complication of reattached body part, unspecified
• Underlying principal diagnosis from index surgery (e.g., C02.9)

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Example 6 — Urology / Perineal Reconstruction

Clinical Scenario: Male patient with Fournier’s gangrene requiring extensive debridement and eventual perineal/scrotal skin loss. After serial debridements, plastic surgery performs free ALT fasciocutaneous flap reconstruction of the perineum and scrotum.

CPT Codes:

• 15757 — Free ALT fasciocutaneous flap with microvascular anastomosis
• 54700 — Incision and drainage of scrotum (prior session — not billed same day)

ICD-10-CM:

• N49.3 — Fournier gangrene (principal)
• E11.69 — Type 2 diabetes with other specified complication (if applicable — HCC 18)
• L98.499 — Non-pressure chronic ulcer of skin of other sites (residual wound if applicable)

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⚠️ Common Coding Pitfalls

• 15756 vs. 15757 selection — The single most common error. Read the operative report carefully: if the surgeon harvested muscle with the flap (e.g., took a cuff of vastus lateralis with the ALT, or included rectus abdominis), the code is 15756. If the flap is skin + fat ± fascia only with no muscle, code 15757. Misidentification shifts wRVU by over 5 units.
• DIEP vs. Free TRAM — DIEP = 15757 (no muscle); Free TRAM = 15756 (muscle included). Surgeons sometimes document both; clarify if documentation is ambiguous.
• 15757 vs. 15758 — 15758 is used for fascial flaps without a skin paddle (e.g., free temporoparietal fascial flap). If a skin paddle is included, 15757 is correct.
• Do not separately bill microvascular anastomosis — The anastomosis is integral to 15757 and not separately billable.
• Modifier -22 requires supporting documentation. A brief operative note mentioning prior radiation or obesity is not sufficient — the note must describe specific additional time, difficulty, or decision-making. Attach a cover letter and expect payer scrutiny.
• Global period violations — Any related procedure performed within 90 days of 15757 requires modifier -78 (related) or -79 (unrelated). Failure to append modifiers may result in claim denial or overpayment recovery.
• Inpatient setting — Never assign CPT in the inpatient acute care setting. Use ICD-10-PCS. The free flap maps to root operation Replacement with autologous tissue, with separate codes for donor site and recipient site.

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📚 Brief Source References

^{AMA CPT Professional Edition 2025, codes 15757–15758 and integumentary surgery guidelines CMS Medicare Physician Fee Schedule Final Rule 2025 – RVU and indicator files (www.cms.gov/Medicare/Medicare-Fee-for-Service-Payment/PhysicianFeeSched) CMS NCCI Policy Manual for Medicare Services, Chapter 7: Surgery – Skin, Subcutaneous & Accessory Structures, 2025 CMS MS-DRG Definitions Manual v41 FY2024, Chapter 6 – Diseases & Disorders of the Skin ICD-10-PCS Official Guidelines for Coding and Reporting FY2025, Section B3 – Root Operations (Replacement, Transfer) ICD-10-CM Official Guidelines for Coding and Reporting FY2025, Section I.C.2 – Neoplasms AAPC CPC/CIC Study Guide – Integumentary & Reconstructive Surgery chapters Wei FC, Mardini S. Flaps and Reconstructive Surgery, 2nd ed. Elsevier 2017 – Fasciocutaneous Free Flaps chapter}