11646

🔪 CPT 11646 — Excision, Malignant Lesion Including Margins, Face, Ears, Eyelids, Nose, Lips; Excised Diameter Over 4.0 cm

Quick Reference

wRVU: 3.13 | Global Period: 090 (90 days) | Assistant Payable: ✅ Yes | Bilateral Indicator: 1

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📋 Clinical Description

CPT 11646 describes the full-thickness excision of a malignant skin lesion — including clinically measured margins — located on the face, ears, eyelids, nose, or lips, where the total excised diameter exceeds 4.0 cm. This is the highest-intensity code in the facial malignant lesion family (11640-11646), selected only when the combined measurement of lesion plus margin clearance results in a specimen diameter greater than 4.0 cm. It is distinct from 11644 (excised diameter 3.1-4.0 cm) and 11643 (2.1-3.0 cm); the operative note or pathology report must document the total excised diameter to select the correct code in the series.

Malignant skin lesions of the face and periocular region — including basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma — are epithelial or melanocytic neoplasms arising from the skin layers of cosmetically and functionally critical anatomic zones. Because these sites involve structures such as eyelid margins, nasal ala, and helical rim, incomplete excision carries high risk of disfigurement, functional impairment (e.g., eyelid retraction, vision obstruction), and local recurrence. When melanoma is the underlying diagnosis, the etiology-specific ICD-10-CM codes from category C43.- drive code selection rather than the C44.- (other malignant neoplasm of skin) series.

This procedure may be performed in the following clinical contexts:

• Large primary BCC or SCC of the face — When biopsy confirms malignancy and the measured excision including margins exceeds 4.0 cm, necessitating this top-tier code in the family.
• Recurrent malignant lesion requiring wider re-excision — Re-excision after previously positive or close margins may produce a final excised diameter exceeding 4.0 cm, driving a step-up to this code.
• Malignant lesion of the eyelid or periocular skin — Excision of large periocular lesions (e.g., large morpheaform BCC of the lower eyelid) performed by an ophthalmologist or oculoplastic surgeon; eyelid-specific modifiers (-E1--E4) apply to identify exact lid quadrant.
• Malignant lesion of the ear or auricle — Large auricular or periauricular SCC frequently requires wide margins given the irregular topography and underlying cartilage involvement; modifier -RT or -LT documents laterality.
• Melanoma of the face, nose, or lip requiring surgical margins — When primary melanoma on the cosmetic subunits of the face requires excision per oncologic margins, C43.- codes are reported; the surgical specimen diameter determines this code vs. sibling codes.

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🔬 Anatomical & Procedural Considerations

Technique Variant	Key Steps / Mechanism	Coding & Clinical Notes
Standard Scalpel Excision	Physician marks margins around the visible lesion, makes a full-thickness elliptical incision through dermis and subcutaneous fat, removes specimen en bloc, and sends for pathological evaluation	Most common technique; total excised diameter = widest diameter of the surgical specimen including margins — measured on the specimen, not the lesion alone
Mohs Micrographic Surgery	Serial horizontal sections with 100% margin evaluation; staged re-excision until clear margins are confirmed	Mohs is reported under 17311-17315 — do NOT report 11646 for Mohs; use 11646 only for standard excision with pathology sent for permanent or frozen section
Repair / Reconstruction	Wound closure after excision — simple (12001-12021), intermediate (12031-12057), or complex (13100-13160); flap or graft (14000-15776)	Repair is separately reportable when performed; the complexity of closure is determined by the closure type, not the lesion size; NCCI policy permits separate reporting
Eyelid-Specific Excision	Full-thickness skin excision at or near the eyelid margin; may involve lamellar reconstruction for anterior lamella defects	Use eyelid anatomic modifiers -E1—E4 to indicate specific eyelid quadrant; large eyelid excisions involving the lid margin may require concurrent reconstruction (separately reportable)

Clinical Pearl

The total excised diameter is measured from the pathology specimen — not from the clinical lesion size visible to the naked eye. The physician must document the pre-excision lesion size AND the total diameter of tissue removed including margins in the operative note. If only the lesion size is documented and no margin measurement is recorded, payers may downcode to a lower sibling code. When pathology returns with positive margins requiring re-excision within the global period, modifier -58 (staged procedure) is appended to the new excision code to bypass the 90-day global window.

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✅ Procedure Includes

• Pre-procedural assessment and measurement of the lesion and planned excision margins
• Local anesthesia infiltration (included; no separate billing)
• Full-thickness skin excision including clinically determined clear margins
• Hemostasis and intraoperative wound management
• Simple closure (linear repair) when performed — note: intermediate/complex closure and flap/graft repair are separately billable
• Specimen submission to pathology for margin evaluation (professional pathology code reported separately by the pathologist)
• Documentation of total excised diameter, lesion location, laterality, and modality in the operative note

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❌ Excludes / Do Not Report Together

Code	Description	Relationship to 11646
11644	Excision, malignant lesion including margins, face, ears, eyelids, nose, lips; excised diameter 3.1-4.0 cm	Sibling code — mutually exclusive based on final excised diameter; report 11644 if the excised specimen measures 3.1-4.0 cm; use 11646 only when diameter exceeds 4.0 cm
11643	Excised diameter 2.1-3.0 cm, same anatomic sites	Sibling code — step below 11644; excised diameter drives which code in the family is reported; only one code in the 11640-11646 series may be reported per lesion
17311	Mohs micrographic surgery, first stage, up to 5 tissue blocks — head, neck, hands, feet, genitalia	Do NOT report 11646 when Mohs technique is used; the Mohs code family (17311-17315) entirely replaces the standard excision code when horizontal margin mapping is performed
12031-13160	Intermediate and complex wound closure / repair	Separately reportable when the wound is closed with layered, complex, or flap technique; simple linear closure is bundled; document closure complexity in the operative note
14000-15776	Adjacent tissue transfer, skin grafts, flap repairs	Separately reportable when a flap or graft is required to achieve wound closure following excision; these represent additional distinct surgical services beyond the excision itself
E/M codes (992xx / 920xx)	Office visit, any level	Separately reportable only when modifier -25 is appended to the E/M code, documenting a significant, separately identifiable E/M service beyond the routine pre-procedure assessment

Bundling Alert — Global Period is 090, Not 010 or 000

CPT 11646 carries a 90-day global surgical package, meaning all routine pre-operative, intraoperative, and post-operative care — including suture removal visits, wound checks, and staple removal — are bundled into the single surgical payment for 90 days post-procedure. This is the most common audit finding in dermatology and surgical practices: billing separate E/M visits for routine wound checks within the 90-day window without a modifier. Any E/M visit for a condition unrelated to the excision during the global window requires modifier -24 appended to the E/M code, with documentation clearly stating the unrelated nature of the visit. Compare this to benign lesion excision codes (11440-11446, same anatomic sites), which carry a 010 global period — billing staff must not apply the shorter global period to 11646 claims.

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🌳 Code Tree — Surgery: Integumentary System, Excision - Malignant Lesions

CPT 11600-11646  Excision — Malignant Lesions (Skin)
│
├── 11600-11606  Excision, malignant lesion including margins — Trunk, Arms, or Legs
│   ├── 11600  Excised diameter 0.5 cm or less
│   ├── 11601  Excised diameter 0.6-1.0 cm
│   ├── 11602  Excised diameter 1.1-2.0 cm
│   ├── 11603  Excised diameter 2.1-3.0 cm
│   ├── 11604  Excised diameter 3.1-4.0 cm
│   └── 11606  Excised diameter over 4.0 cm
│
├── 11620-11626  Excision, malignant lesion including margins — Scalp, Neck, Hands, Feet, Genitalia
│   ├── 11620  Excised diameter 0.5 cm or less
│   ├── 11621  Excised diameter 0.6-1.0 cm
│   ├── 11622  Excised diameter 1.1-2.0 cm
│   ├── 11623  Excised diameter 2.1-3.0 cm
│   ├── 11624  Excised diameter 3.1-4.0 cm
│   └── 11626  Excised diameter over 4.0 cm
│
└── 11640-11646  Excision, malignant lesion including margins — Face, Ears, Eyelids, Nose, Lips
    ├── 11640  Excised diameter 0.5 cm or less  (Global: 090)
    ├── 11641  Excised diameter 0.6-1.0 cm  (Global: 090)
    ├── 11642  Excised diameter 1.1-2.0 cm  (Global: 090)
    ├── 11643  Excised diameter 2.1-3.0 cm  (Global: 090)
    ├── 11644  Excised diameter 3.1-4.0 cm  (Global: 090)
    └── ▶▶ 11646 ◀◀  Excised diameter over 4.0 cm  ← YOU ARE HERE  (Global: 090)

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💰 RVU & Reimbursement Profile

Component	Value
Work RVU (wRVU)	3.13 (verify against current CMS MPFS for applicable year)
Global Period	090 (90 days)
Bilateral Indicator	1 — Subject to standard 150% bilateral payment adjustment rules
Assistant Surgeon	✅ Payable
Co-Surgeon	❌ Not applicable
Team Surgery	❌ Not applicable
PC/TC Split	❌ No — procedure code only (Indicator 0)
Modifier -51 Exempt	No
Anesthesia	Local infiltration anesthesia included in the global payment; no separate anesthesia billing expected for standard excision

Bilateral Billing Rules

11646 has a bilateral indicator of 1, meaning it is subject to the standard Medicare 150% bilateral payment adjustment. When identical facial malignant lesion excisions are performed bilaterally in the same session (e.g., bilateral auricular lesions over 4.0 cm), report with modifier -50 on a single line (1 unit) per Medicare/NCCI policy, or on two lines with -RT and -LT per some commercial payer preferences — verify your MAC’s billing format. Medicare pays the lower of: (a) total actual charges for both sides, or (b) 150% of the fee schedule amount for a single code (100% first side, 50% second side). Note that bilateral facial lesion excisions of this magnitude are clinically uncommon; the more likely scenario involves two separate lesions at different sites, which would be reported with -51 and -59 on separate lines.

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🏷️ Modifier Reference

Modifier	Name	When to Apply
-RT	Right Side	Procedure performed on right ear, right eyelid, right facial subunit, or right nasal ala
-LT	Left Side	Procedure performed on left ear, left eyelid, left facial subunit, or left nasal ala
-50	Bilateral Procedure	Bilateral excisions of the same size tier at bilaterally paired sites (e.g., both ears) during the same session; verify MAC billing format preference
-E1	Upper Left Eyelid	When the malignant lesion is located on the upper left eyelid skin; use in addition to LT for ophthalmology billing
-E2	Lower Left Eyelid	When the malignant lesion is located on the lower left eyelid skin
-E3	Upper Right Eyelid	When the malignant lesion is located on the upper right eyelid skin
-E4	Lower Right Eyelid	When the malignant lesion is located on the lower right eyelid skin
-25	Significant, Separately Identifiable E/M	Applied to the E/M code — not 11646 — when a new or established patient office visit with a separately documented clinical decision-making process is performed on the same date as the excision
-24	Unrelated E/M During Postoperative Period	Applied to the E/M code when a patient returns within the 90-day global window for a condition unrelated to the excision; document the unrelated nature explicitly in the note
-51	Multiple Procedures	When 11646 is performed with other surgical procedures at the same session; apply to the lower-valued code
-59	Distinct Procedural Service	When payers bundle 11646 with another procedure; documents a distinct anatomic site or separate lesion
-52	Reduced Services	Procedure partially completed — document the reason and extent of service reduction
-53	Discontinued Procedure	Procedure stopped due to patient safety concern; document reason thoroughly
-58	Staged or Related Procedure	Planned re-excision for positive margins within the 90-day global period; must be documented as a planned staged procedure
-78	Unplanned Return to OR	Unplanned return to the OR for a complication (e.g., hematoma, dehiscence) within the 90-day global window
-79	Unrelated Procedure During Postoperative Period	Unrelated surgical procedure performed during the 90-day global window; appended to the unrelated procedure code

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🩺 Common ICD-10-CM Pairings

Basal Cell Carcinoma — Eyelid and Periocular

ICD-10 Code	Description	HCC?	Clinical Notes
C44.1121	Basal cell carcinoma of skin of right upper eyelid, including canthus	❌ No	Most specific eyelid BCC code — requires documentation of right side AND upper vs. lower lid; pair with modifier -E3
C44.1122	Basal cell carcinoma of skin of right lower eyelid, including canthus	❌ No	Pair with modifier -E4; lower eyelid BCC is the most common periocular site
C44.1191	Basal cell carcinoma of skin of left upper eyelid, including canthus	❌ No	Pair with modifier -E1 and -LT
C44.1192	Basal cell carcinoma of skin of left lower eyelid, including canthus	❌ No	Pair with modifier -E2 and -LT
C44.111	Basal cell carcinoma of skin of unspecified eyelid, including canthus	❌ No	Use only when laterality AND upper/lower designation are entirely absent from documentation; query provider before defaulting to unspecified

Basal Cell Carcinoma — Face, Ear, Nose, Lip

ICD-10 Code	Description	HCC?	Clinical Notes
C44.212	Basal cell carcinoma of skin of right ear and external auricular canal	❌ No	Pair with -RT; includes auricular skin and canal — document whether cartilage invasion is present as it may affect reconstruction coding
C44.219	Basal cell carcinoma of skin of left ear and external auricular canal	❌ No	Pair with -LT
C44.311	Basal cell carcinoma of skin of nose	❌ No	No laterality distinction for nasal skin BCC at this specificity level; document nasal subunit in clinical note
C44.319	Basal cell carcinoma of other parts of face	❌ No	Use for cheek, chin, forehead, temple, and other facial subunits not captured by more specific codes; “other parts of face” is appropriate when no more specific code exists
C44.01	Basal cell carcinoma of skin of lip	❌ No	Applies to cutaneous (skin) surface of lip — not mucosal lip; mucosal lip malignancies code to C00.-

Squamous Cell Carcinoma — Face, Ear, Eyelid

ICD-10 Code	Description	HCC?	Clinical Notes
C44.1221	Squamous cell carcinoma of skin of right upper eyelid, including canthus	❌ No	Pair with -E3 and -RT; SCC of eyelid is less common than BCC but carries higher metastatic risk
C44.1222	Squamous cell carcinoma of skin of right lower eyelid, including canthus	❌ No	Pair with -E4 and -RT
C44.1291	Squamous cell carcinoma of skin of left upper eyelid, including canthus	❌ No	Pair with -E1 and -LT
C44.1292	Squamous cell carcinoma of skin of left lower eyelid, including canthus	❌ No	Pair with -E2 and -LT
C44.222	Squamous cell carcinoma of skin of right ear and external auricular canal	❌ No	SCC of the auricle has higher nodal spread risk; verify whether sentinel lymph node biopsy is also performed (separately reported)
C44.02	Squamous cell carcinoma of skin of lip	❌ No	Cutaneous lip SCC — confirm documentation specifies skin surface; mucosal SCC codes to C00.-

Melanoma — Face and Periocular

ICD-10 Code	Description	HCC?	Clinical Notes
C43.111	Malignant melanoma of unspecified eyelid, including canthus	✅ HCC	Use C43.- series — NOT C44.- — for all melanoma diagnoses; HCC-relevant; query for Breslow depth and Clark level for inpatient records
C43.121	Malignant melanoma of right upper eyelid, including canthus	✅ HCC	Most specific right upper lid melanoma code — pair with -E3 and -RT
C43.122	Malignant melanoma of right lower eyelid, including canthus	✅ HCC	Pair with -E4 and -RT
C43.191	Malignant melanoma of left upper eyelid, including canthus	✅ HCC	Pair with -E1 and -LT
C43.192	Malignant melanoma of left lower eyelid, including canthus	✅ HCC	Pair with -E2 and -LT
C43.31	Malignant melanoma of nose	✅ HCC	No right/left axis for nasal skin melanoma; document subsite for clinical completeness

Underlying Etiology / History / Complication Codes

ICD-10 Code	Description	HCC?	Clinical Notes
Z85.828	Personal history of other malignant neoplasm of skin	❌ No	Report as secondary diagnosis when prior skin cancer history is documented and clinically relevant to the current encounter; supports medical necessity for wide margins
Z77.098	Contact with and (suspected) exposure to other hazardous, chiefly nonmedicinal, chemicals	❌ No	Report as additional code when UV/chemical exposure is explicitly documented as contributing etiology and clinically affects treatment planning
L57.0	Actinic keratosis	❌ No	Report as additional diagnosis when the provider documents concurrent actinic keratoses in the same region; do not confuse with the primary malignancy — this is a precursor/comorbid lesion

Coding Specificity Reminder

For malignant skin lesions of the eyelid (C43.- and C44.-), ICD-10-CM requires four levels of specificity: (1) malignancy type (BCC, SCC, melanoma, other), (2) site (eyelid vs. other facial subunit), (3) laterality (right vs. left), AND (4) upper vs. lower eyelid. All four characters are required to assign the most specific code — defaulting to “unspecified eyelid” or “unspecified side” without a provider query is not acceptable coding practice. The unspecified codes exist only for cases where documentation is genuinely absent after a query attempt has been made and documented per your facility’s CDI policy.

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🏥 MS-DRG Considerations (Inpatient)

Inpatient Coding Reminder

CPT 11646 is performed primarily in the outpatient, office, or ASC setting. There are no routine MS-DRG assignments for this procedure — inpatient admission solely for malignant skin lesion excision of the face would not be supported by any payer, MAC, or utilization review body under standard clinical guidelines. If a patient undergoing an inpatient admission for an unrelated diagnosis (e.g., advanced melanoma with systemic involvement, or post-operative complication) also has a skin lesion excised, an ICD-10-PCS code may be assigned for facility completeness. For inpatient admissions driven by melanoma with metastatic disease, the relevant DRG family is within MDC 09 (Diseases and Disorders of the Skin, Subcutaneous Tissue and Breast) — DRGs 573-578 — with CC/MCC tier adjustment.

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🔧 ICD-10-PCS Equivalents (Inpatient Facility Coding)

Note

Inpatient PCS coding for facial skin excision is uncommon and will rarely affect DRG assignment unless the excision is incidental to a longer inpatient stay driven by a different principal diagnosis. The PCS root operation is Excision (B) — cutting out or off, without replacement, a portion of a body part — consistent with excision of a defined lesion area. If the entire skin of an anatomic region were removed, Resection (T) would apply, but this is not applicable to skin lesion excision. Assign separate PCS code lines for right vs. left when bilateral.

PCS Code	Full Description	Applicable Modality
0HB1XZZ	Excision of Face Skin, External Approach, No Device, No Qualifier	Standard scalpel excision, facial skin (forehead, cheek, chin, nose)
0HB2XZZ	Excision of Right Ear Skin, External Approach, No Device, No Qualifier	Excision of right auricular/periauricular skin
0HB3XZZ	Excision of Left Ear Skin, External Approach, No Device, No Qualifier	Excision of left auricular/periauricular skin
0HB4XZZ	Excision of Right Upper Eyelid, External Approach, No Device, No Qualifier	Eyelid skin excision, right upper lid
0HB5XZZ	Excision of Left Upper Eyelid, External Approach, No Device, No Qualifier	Eyelid skin excision, left upper lid
0HBAXZZ	Excision of Upper Lip Skin, External Approach, No Device, No Qualifier	Cutaneous upper lip excision
0HBBXZZ	Excision of Lower Lip Skin, External Approach, No Device, No Qualifier	Cutaneous lower lip excision

PCS Character Analysis — 0HB1XZZ

Position	Character	Value	Definition
1	Section	0	Medical and Surgical
2	Body System	H	Skin and Breast
3	Root Operation	B	Excision (cutting out or off, without replacement, a portion of a body part)
4	Body Part	1	Skin, Face
5	Approach	X	External (procedures performed directly on the skin or mucous membrane)
6	Device	Z	No Device
7	Qualifier	Z	No Qualifier

PCS Root Operation: Excision (B) vs. Resection (T)

• Use Excision (B) when a defined lesion area — including margins — is removed but the remaining skin of the body part is preserved; this applies to all lesion excision scenarios coded under CPT 11640-11646.
• Use Resection (T) only when the entire body part (e.g., entire eyelid) is removed; this is not applicable in the context of lesion excision.
• When bilateral skin lesions are excised, assign separate PCS code lines for each side treated — PCS has no modifier equivalent for bilateral procedures.

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📝 Coding Examples

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Example 1 — Office: Large BCC of the Left Lower Eyelid

Clinical Scenario: A 74-year-old male presents with a biopsy-confirmed morpheaform basal cell carcinoma of the left lower eyelid. The dermatologist documents a lesion measuring approximately 3.2 cm with planned 6 mm margins on all sides. The operative note states: “Excision of left lower eyelid BCC with margins; total excised specimen diameter measured 4.4 cm.” The wound was closed primarily with layered closure. A separate E/M was documented noting the patient’s new concern about a separate solar lentigo on the scalp (no treatment performed today).

Field	Code	Rationale
CPT 1	11646-LT-E2	Malignant lesion excision, face/eyelid site, excised diameter 4.4 cm = over 4.0 cm threshold; LT for left side, E2 for lower left eyelid
CPT 2	12032-LT	Intermediate layered closure, 2.6-7.5 cm; reported separately as wound complexity exceeds simple closure; LT modifier for laterality
CPT 3	99213-25	Established patient office visit, low complexity — separately identifiable E/M for the unrelated scalp lesion evaluation; -25 on the E/M code, not on 11646
PDx	C44.1192	BCC of skin of left lower eyelid, including canthus — most specific available code matching documentation

Note

Modifier -25 belongs on the E/M code (99213), not on the procedure code (11646). The E/M documentation must reflect a separately identifiable service — in this case, evaluation of a distinct new concern. If the E/M note addresses only pre-procedure assessment for the eyelid BCC, the -25 modifier cannot be supported and the E/M is not separately billable.

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Example 2 — ASC: Bilateral Auricular SCC, Same Session

Clinical Scenario: A 68-year-old female with extensive sun exposure history presents for same-day excision of biopsy-confirmed SCC of both ears. The operative note documents: right auricle excision with total specimen diameter 4.6 cm; left auricle excision with total specimen diameter 4.3 cm. Both wounds required intermediate repair. No separate E/M was documented.

Field	Code	Rationale
CPT 1	11646-RT	Right auricular SCC excision, excised diameter over 4.0 cm; primary procedure, higher RVU side
CPT 2	11646-LT-51	Left auricular SCC excision, excised diameter over 4.0 cm; modifier -51 on the second (lower-valued) procedure per multiple procedure rules
CPT 3	12034-RT	Intermediate closure, right ear wound
CPT 4	12034-LT-51	Intermediate closure, left ear wound
PDx	C44.222	SCC of skin of right ear and external auricular canal
SDx	C44.229	SCC of skin of left ear and external auricular canal

Warning

Do NOT use modifier -50 for bilateral procedures when the two lesions are separately described in the operative note with individual specimen measurements — report on separate lines with RT and LT. Modifier -50 is appropriate only when the procedure is performed as a single bilateral service without distinguishable laterality documentation. Billing both lines without modifier -51 on the second line risks an NCCI edit overpayment finding on audit.

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Example 3 — Office: Re-Excision for Positive Margins (Global Period / Staged Procedure)

Clinical Scenario: A 71-year-old male undergoes excision of a 4.2 cm BCC of the right cheek (CPT 11646-RT reported on 03/01/2026). Pathology returns with positive deep margin. On 03/14/2026 — within the 90-day global window — the physician performs planned re-excision to achieve clear margins; the second specimen measures 2.2 cm. The operative note states: “Staged re-excision, right cheek BCC, planned secondary procedure for positive margins.” A routine wound check was also conducted at the same visit.

Field	Code	Rationale
CPT 1	11643-RT-58	Re-excision of right cheek BCC; new excised diameter 2.2 cm = 11643 range (2.1-3.0 cm); modifier -58 indicates staged/related procedure within global period of original 11646
PDx	C44.319	BCC of other parts of face (right cheek); continues to be the primary diagnosis driving the procedure
SDx	Z85.828	Personal history of malignant neoplasm of skin — documents prior treated lesion history supporting medical necessity of staged re-excision

Note

Global period reminder: The original 11646 reported on 03/01/2026 opens a 90-day global window through 05/30/2026. Any routine wound check visits within that window are bundled — do not report E/M separately for wound checks. The re-excision on 03/14/2026 is a planned staged procedure (modifier -58), which bypasses the global bundle and opens a NEW 90-day global period from the date of the re-excision. The new re-excision is coded based on the NEW specimen diameter, not the original lesion size — note the step-down to 11643 based on the smaller second specimen.

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⚠️ Common Coding Pitfalls

• Missing or incomplete excised diameter documentation: The single most common downcoding trigger for the 11640-11646 family. The physician must document the total excised diameter (lesion plus margins), not just the lesion size. If only the clinical lesion size is documented without a measured excision diameter, payers will default to the smallest code in the series. The operative note or pathology report must contain a measurable diameter value; the phrase “excised with adequate margins” is not sufficient.

• Reporting 11646 for Mohs surgery: CPT 11646 is a standard excision code — Mohs micrographic surgery (17311-17315) is an entirely separate code family with distinct technique requirements (horizontal tissue sections, same-day margin evaluation, surgeon serving as both surgeon and pathologist). Billing 11646 when Mohs technique was performed is a material misrepresentation of service. Confirm the operative note technique before selecting the code series.

• Billing -25 on the procedure code rather than the E/M code: Modifier -25 must always be appended to the evaluation and management code, never to the surgical code. Additionally, the E/M documentation must stand independently of the pre-procedure evaluation — it cannot simply restate the decision to proceed with surgery. A common audit finding is -25 appended to 11646 itself, which will produce a claim edit or denial.

• Reporting separate E/M for routine post-op wound checks within the 90-day global: CPT 11646 carries a 90-day global surgical package. Post-operative wound checks, suture removal, and scar assessment within 90 days are bundled. Billing E/M codes for these visits without modifier -24 (unrelated condition) creates overpayment liability subject to RAC and MAC audit. Implement a date-of-service flag in your billing system at the time of the procedure to prevent automatic E/M generation during the global window.

• Defaulting to unspecified ICD-10-CM without querying: For eyelid lesions specifically, ICD-10-CM requires malignancy type + site + laterality + upper/lower designation. Defaulting to C44.111 (unspecified eyelid, unspecified laterality) without a CDI query when the operative note clearly states “right lower eyelid” is a documentation capture failure. The more specific code is almost always available and should be assigned; unspecified codes are a last resort after a genuine query attempt.

• Confusing the facial malignant code family (11640-11646) with the trunk/arms/legs family (11600-11606) or scalp/neck family (11620-11626): These three anatomic families have different RVU profiles and are location-specific. A cheek or eyelid lesion codes to 11640-11646, NOT to 11600-11606. Similarly, a scalp lesion does not code to 11640-11646. Anatomic site is a required code selection element and must be explicitly documented.

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📎 Sources

¹ AMA CPT 2025 Professional Edition — CPT 11646, Surgery: Integumentary System, Excision-Malignant Lesions · ² CMS 2025 Medicare Physician Fee Schedule Final Rule (CMS-1807-F) · ³ CMS RVU25A Relative Value Files — wRVU and bilateral indicator data for CPT 11646 · ⁴ NCCI Policy Manual Chapter 4 (Surgery: Integumentary System), CMS 2025 — bundling rules for excision and repair codes · ⁵ ICD-10-CM Official Guidelines for Coding and Reporting FY2026 — Chapter 2: Neoplasms, C43-C44 coding guidance · ⁶ ICD-10-PCS Official Guidelines for Coding and Reporting FY2026 — Root Operation Excision (B), Body System H (Skin and Breast) · ⁷ CMS Medicare Coverage Database Article A57660 — Billing and Coding: Excision of Malignant Skin Lesions · ⁸ AAPC CPT Code 11646 Reference — aapc.com/codes/cpt-codes/11646 · ⁹ AAFP — “Skin Deep: How to Properly Code for Biopsies and Lesion Removal,” Family Practice Management, March 2019 · ¹⁰ Palmetto GBA Jurisdiction M — Bilateral Procedures and Modifiers Policy (2024) · ¹¹ AAPC Dermatology Coding Alert — Malignant Skin Lesion Excision Series 11600-11646 Coding Guidelines