CPT Code 11640: Excision of malignant lesion, face, 0.5 cm or less

Key Takeaways

CPT Code 11640 describes excision of a malignant lesion including margins on the face, ears, eyelids, nose, or lips with an excised diameter of 0.5 cm or less.

Excised diameter is measured as the lesion’s widest dimension plus the narrowest margin required for adequate excision, not the largest margin.

Pathology confirmation of malignancy is required for medical necessity; billing without it is a False Claims Act risk.

Pabau’s claims management software helps dermatology and plastic surgery practices track excision codes, modifiers, and documentation requirements to reduce claim denials.

CPT Code 11640 covers excision of a malignant lesion, including margins, on the face, ears, eyelids, nose, or lips when the excised diameter is 0.5 cm or less.

Dermatologists, plastic surgeons, and otolaryngologists are the primary billers for this code. Each specialty brings slightly different documentation habits, and those differences show up clearly in Medicare audit data. Understanding where those risks concentrate helps practices tighten workflows before claims go out the door.

CPT Code 11640: Definition and clinical description

CPT Code 11640, as maintained by the American Medical Association (AMA), describes the excision of a malignant lesion including margins located on the face, ears, eyelids, nose, or lips when the excised diameter is 0.5 cm or less.

The code sits within the Integumentary System section of the CPT codebook, specifically in the Excision-Malignant Lesions subsection (11600-11646).

These anatomic sites share something important: they are cosmetically and functionally sensitive. Eyelids protect the globe. The nose and lips affect both aesthetics and function. That sensitivity is why the 11640-11646 series exists as a separate code family from the 11600-11606 series, which covers trunk, scalp, arms, and legs.

When to use CPT Code 11640: Clinical indications

This code applies when a clinician excises a confirmed or suspected malignant lesion from a facial, auricular, periorbital, nasal, or labial site. The most common diagnoses are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), though melanoma on these sites also triggers the series.

Practices using dermatology EMR software like Pabau’s can flag these cases automatically for code review before billing.

Three conditions must be present for 11640 to apply:

• The lesion is on one of the five named anatomic sites (face, ears, eyelids, nose, or lips)
• Malignancy is confirmed or clinically suspected (with pathology ordered)
• The excised specimen diameter, including the narrowest required margin, is 0.5 cm or less

Plastic surgeons billing facial reconstructive procedures and ENT specialists removing periauricular lesions also use this code. If the lesion is on the scalp, trunk, or extremities, the correct series is 11600-11606, not 11640-11646. Plastic surgery EMR systems that support anatomic site selection at the point of documentation reduce this type of site-of-service coding error.

How to measure excised diameter for CPT Code 11640

The most litigated element of 11640 billing is the diameter measurement. The AMA rule is specific: excised diameter equals the widest dimension of the lesion plus the most narrow margin required for adequate excision of that lesion. The narrowest margin drives the measurement, not the average or widest.

This matters because many coders measure the visible lesion alone and add a standard margin estimate. That method is wrong and is a top audit trigger under the OIG Work Plan. The operative note must document both the lesion size and the specimen size including margins.

• Step 1: Record the widest clinical dimension of the lesion before excision
• Step 2: Identify the narrowest margin required for complete excision (pathologically adequate)
• Step 3: Add widest lesion dimension + narrowest margin to get excised diameter
• Step 4: Select the code matching that total (see the series comparison table below)

A 0.3 cm BCC requiring a 0.1 cm minimum margin produces an excised diameter of 0.4 cm, correctly placing the claim under 11640. The same lesion with a 0.3 cm margin produces 0.6 cm, which pushes it to CPT 11641. The margin decision is clinical, but it must be documented precisely.

CPT Code 11640 vs related codes in the 11640-11646 series

CPT codes 11640 through 11646 cover all malignant excisions on face, ears, eyelids, nose, and lips, differentiated only by excised diameter. Selecting the wrong size tier is the most common upcoding violation cited in dermatology audits.

Note that 11645 does not exist in the current CPT schedule; the series jumps from 11644 to 11646. Billing 11645 produces an automatic rejection.

ICD-10 codes commonly paired with CPT Code 11640

Per CMS LCD guidance, the ICD-10-CM diagnosis code must confirm malignancy at the correct anatomic sub-site, and pathology confirmation is required before a malignant diagnosis code is assigned. The CMS ICD-10 codes page has the current-year update files and official guidelines.

Specificity matters. C44.319 (unspecified face) is acceptable when the sub-site is genuinely ambiguous, but using it for a clearly documented nasal or eyelid lesion is a coding error. Payers can deny on specificity alone.

Modifiers for CPT Code 11640

Modifier selection for 11640 is one of the areas where billing staff most frequently ask questions, and incorrect application creates denial patterns that draw payer audits. The same modifier logic applies to CPT 17314, the Mohs micrographic surgery code used on many of the same facial sites. The table below covers the modifiers most commonly applied to 11640.

Medicare does not accept modifier -51 on all codes. Verify that 11640 is not exempt from multiple procedure reduction rules under the applicable fee schedule before applying -51.

CPT Code 11640 Medicare reimbursement and fee schedule

Medicare reimbursement for CPT Code 11640 is calculated using the Resource-Based Relative Value Scale (RBRVS). Payment equals the total RVU multiplied by the geographic conversion factor for the practice’s locality, so no single national dollar figure applies.

Use the CMS fee schedule lookup or the FastRVU 2026 RVU lookup to calculate the rate for your specific locality.

The table below compares how RVU components for 11640 differ between non-facility and facility settings. Dollar amounts depend on the current year’s conversion factor and geographic practice cost index (GPCI) adjustments for your locality.

Facility vs non-facility rates for CPT 11640

The site of service significantly affects payment. When performed in the physician’s office (place of service code 11), the practice absorbs overhead costs and receives the non-facility rate, which is higher.

When performed in an ambulatory surgery center (ASC, place of service code 24) or hospital outpatient department, the facility absorbs those overhead costs and Medicare pays the lower facility rate to the physician. Billing the wrong place of service code is a CMS compliance risk and is flagged by NCCI edits.

Documentation requirements to bill CPT Code 11640

Per First Coast Service Options’ LCD Article A57660 (practices in other jurisdictions should check the equivalent LCD from their own MAC), the medical record must include specific elements before an 11640 claim passes medical necessity review. Missing any of them is grounds for denial or post-payment recoupment.

Practices using patient intake software can build 11640-specific operative templates that prompt for every required field.

• Pre-operative diagnosis: Malignancy confirmed by prior biopsy pathology or clinically suspected with pathology ordered
• Anatomic location: Specific sub-site documented (e.g., left lower eyelid, right nasal ala, upper lip vermillion border)
• Lesion size: Widest clinical dimension of the lesion before excision
• Specimen size: Total excised specimen dimensions including margins as measured by the operating clinician
• Operative note: Procedure description confirming excision method, closure type, and specimen handling
• Post-operative pathology report: Confirming malignancy and margin status

Billing without post-operative pathology confirmation creates False Claims Act exposure. If the pathology returns benign, the claim must be corrected to a benign excision code such as 11444. Some practices bill before pathology returns; that is acceptable only if the pre-operative diagnosis supports malignancy and the record is updated once pathology comes back.

Reduce claim denials with smarter documentation workflows

Pabau's claims management software helps dermatology and plastic surgery practices track excision codes, apply correct modifiers, and ensure documentation is complete before claims go out. See how it works for skin cancer billing workflows.

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Can CPT Code 11640 be billed with repair or closure codes?

Simple closure is bundled into 11640 and not separately billable. The AMA CPT guidelines are explicit: the excision codes in the 11600-11646 series include simple (linear) closure as part of the procedure. Billing a simple repair code from the 12001-12018 range, such as 12007, alongside 11640 without a modifier is an NCCI edit violation.

However, two types of repair ARE separately billable when performed at the same session:

• Intermediate or complex repair (12031-12047, 13100-13160), such as 12037: billable separately when the wound requires layered closure or complex technique. Apply modifier -59 to the repair code to override the NCCI edit. Verify current NCCI edit pairs before billing, as edit status changes annually.
• Adjacent tissue transfer (14060, 14061): billable separately when a local flap is required for wound closure after an excision on the eyelids, nose, ears, or lips. CPT 14060 covers a defect of 10 sq cm or less; 14061 covers a defect of 10.1-30 sq cm. These are common after eyelid and nasal excisions where primary closure is not achievable. Modifier -59 applies.

The test is whether the repair required a level of complexity or technique above simple closure. If the answer is yes and the operative note documents that, separate billing is appropriate. If the note just says “wound closed,” separate billing will not survive audit.

Common billing errors and audit risks for CPT 11640

The OIG Work Plan and Medicare audit data identify recurring error patterns for facial malignant excision codes. A practice billing 11640 with clean individual records can still be flagged if its pattern across the 11640-11646 series looks statistically unusual — the same scrutiny applies to 11603, the trunk, arm, and leg counterpart series.

• Measuring the lesion, not the specimen: Using the pre-excision lesion size rather than the excised specimen size including margins understates the true excised diameter and may incorrectly place the claim in 11640 when 11641 is correct, or vice versa.
• Missing pathology confirmation: Billing a malignant code without a pathology report on file creates False Claims Act exposure. The report does not need to be received before billing, but it must be ordered and documented pre-operatively.
• Incorrect anatomic site code: Billing 11640 for a trunk or extremity lesion; those require the 11600-11606 series. The anatomic site in the operative note must match the code selected.
• Unbundling simple closure: Adding a simple repair code (12001-12018) to 11640 without modifier -59 and clinical justification violates NCCI edits.
• Failing to apply modifier -51: Billing multiple excisions on the same day without modifier -51 on secondary codes overstates reimbursement.
• Upcoding to a higher size tier: Documenting specimen size as 0.6 cm when the measured excised diameter is 0.4 cm shifts the claim from 11640 to 11641 without clinical basis. This is a top audit trigger when a practice’s 11641 rate is disproportionate to its 11640 rate.

A practice-level audit check: compare the ratio of 11640 to 11641 claims over any 90-day period. If 11641 accounts for more than 70% of all claims in the series, that imbalance warrants a documentation review before a payer flags it.

Billing CPT 11640 in dermatology practice management

Practices billing 11640 regularly benefit from workflow tools that connect the operating suite to the billing office. The most common breakdown point is the operative note: a clinician documents lesion size but omits specimen size, or records specimen dimensions without specifying whether margins are included.

Structured clinical note templates prompt clinicians to record both values at the point of care. That documentation then flows directly into the billing workflow, reducing the back-and-forth between coders and clinicians that delays claims.

London Face and Skin Clinic, a UK medi-aesthetic practice, went fully paperless after switching to a single system, as this case study shows.

Pabau’s claims management software supports practices in tracking excision code utilization, flagging incomplete documentation before submission, and monitoring modifier usage patterns by provider.

Conclusion

CPT Code 11640 carries audit risk because the measurement rule is specific, the pathology requirement is strict, and payers actively monitor the distribution of claims across the 11640-11646 series.

Getting the excised diameter calculation right, matching the correct ICD-10 sub-site, and keeping the pathology report on file before or shortly after billing are the three highest-priority controls for any practice billing this code regularly.

Pabau’s claims management software helps skin cancer and dermatology practices build those controls into their daily workflow. To see how the documentation and billing features work together for excision code management, book a demo with the Pabau team.

Continue your research

Treating facial skin cancer with Mohs surgery instead of excision? CPT Code 17314 covers Mohs micrographic surgery billing, modifiers, and Medicare rates for the same anatomic sites.

Working across multiple procedure code series? Bupa CCSD procedure codes illustrates how different coding systems handle site-specific excision procedures.

Frequently Asked Questions