CPT code 11604 – Excision of malignant lesion, trunk, arms, and legs

Key takeaways

CPT code 11604 covers excision of a malignant lesion on the trunk, arms, or legs with an excised diameter of 3.1 to 4.0 cm.

Excised diameter equals the lesion’s widest dimension plus the narrowest surgical margin on each side, measured before excision.

Simple (linear) closure is bundled into 11604, while intermediate and complex repairs are reported separately.

Every 11604 claim needs a confirmed malignant diagnosis from pathology, so hold the claim until the report returns.

A clearly written diameter calculation in the operative note is the best defense against downcoding and denials.

CPT code 11604: Official descriptor and procedure overview

CPT code 11604 is the procedure code for excising a malignant skin lesion, margins included, on the trunk, arms, or legs.

It applies when the excised diameter is 3.1 to 4.0 cm. The official descriptor from the American Medical Association (AMA) reads: Excision, malignant lesion including margins, trunk, arms, or legs; excised diameter 3.1 to 4.0 cm. In plain terms, the excised diameter has to be over 3.0 cm and no more than 4.0 cm.

The code sits in the Integumentary System section of CPT (10004-19499). Within it, 11600 to 11606 cover malignant lesion excision on the trunk and extremities.

How the excised diameter is measured for CPT code 11604

The excised diameter for CPT code 11604 equals the widest diameter of the visible lesion plus the narrowest surgical margin on each side. It is measured before the specimen is removed. This is the AMA’s published method from CPT Assistant guidance. The pathology lab’s specimen measurement is a different number.

A worked example illustrates where 11603 ends and 11604 begins.

The 11604 range starts above 3.0 cm, so an excised diameter of exactly 3.0 cm belongs to 11603. Auditors look for the calculation in the operative note. A note that says “approximately 3 cm” without the margin arithmetic leaves the claim open to downcoding or denial.

Key rule: Use the pre-excision measurement, not the specimen measurement after formalin fixation. Tissue contracts in fixative, so the specimen will typically measure smaller than the pre-excision diameter.

Anatomic sites covered by CPT code 11604 (and what is excluded)

CPT code 11604 applies to malignant lesions on the trunk, arms, and legs, as the AMA defines those regions for coding. Knowing the boundaries prevents a common site-selection error. That error is picking a trunk or extremity code for a lesion on the scalp, face, or hand.

Included sites (use 11600-11606):

• Trunk: Chest wall, abdomen, back, buttocks, perineum
• Upper extremities: Shoulder, upper arm, elbow, forearm (excluding hands)
• Lower extremities: Thigh, knee, lower leg (excluding feet)

Excluded sites (use different code series):

Record the anatomic site in the operative note in the code set’s own terms. Write “left posterior shoulder,” for example, rather than “upper back area.” The coder can then match the site to the right code series without querying the surgeon.

CPT 11604 in the malignant excision code family: Choosing the right code

The 11600-series codes for trunk, arms, and legs are selected solely by excised diameter. There are no separate codes for technique, malignancy subtype, or number of margins taken.

There is no 11605 in the code set, so the series jumps from 11604 straight to 11606. A measurement of exactly 4.0 cm still falls under 11604. Only measurements over 4.0 cm shift to 11606. The chart below maps each excised diameter to its code.

11604 vs 11603 and 11606: Avoiding threshold errors

Auditors concentrate on measurements within 1 mm of the 3.0 cm and 4.0 cm boundaries. A documented excised diameter of 3.1 cm sits just 1 mm above 11603, so expect a careful review. The operative note must state the lesion diameter, each margin, and the total, all in centimeters.

For borderline measurements, document the margin selection rationale. Oncologic margins for basal cell carcinoma typically range from 0.3 to 0.5 cm, while squamous cell carcinoma may require 0.5 to 1.0 cm. A note that explains the clinical basis for the margin width gives the auditor context rather than just a number.

Repair codes and add-on codes that can be billed with CPT code 11604

Simple (linear) closure is bundled into CPT code 11604 and cannot be billed separately under any modifier. Billing a simple repair code (12001-12021) with 11604 for the same wound breaks National Correct Coding Initiative (NCCI) bundling rules. Payers deny the repair code automatically.

An intermediate or complex repair code only holds up when the note describes the closure. Layered closure, undermining, or other complex technique should be named in the note, along with the length of the repaired wound.

ICD-10-CM diagnosis codes used with CPT code 11604

Every CPT code 11604 claim requires a confirmed malignant diagnosis code from the ICD-10-CM code set. Payers will not accept a “rule out” or “suspected” diagnosis for a malignant excision code. The pathology report must confirm malignancy, and the diagnosis code must reflect that finding.

Select the most specific code available by site, laterality, and histologic type. Unspecified codes are acceptable when documentation supports nothing more specific, but some commercial payers send them for medical necessity review. Use the confirmed pathology report, not the pre-operative impression, to select the diagnosis code for the final claim.

Surgical pathology and CPT 88305: The companion pathology code for malignant excisions

Every malignant lesion excision must be accompanied by submission of the specimen to a pathology lab. The standard code for skin lesion specimens is 88305, Level IV surgical pathology with gross and microscopic examination.

• Who bills 88305: The pathology laboratory, not the performing surgeon
• Surgeon’s responsibility: The operative note must document that the specimen went to pathology, including the specimen label and container details
• Claim adjudication: The malignant ICD-10-CM code must match the pathology report, and payers can request that report on review
• Timing: The claim should carry the confirmed malignant diagnosis, so hold it until the pathology report returns

Documentation requirements to support a CPT code 11604 claim

A missing excised diameter calculation is a frequent audit finding on CPT code 11604 claims. Payers treat a note that omits the arithmetic like a note with no measurement at all. The claim gets denied or downcoded.

Before billing, confirm the operative note contains all of these elements. Practices focused on submitting a clean claim build this checklist into their pre-submission workflow.

• Pre-excision lesion dimensions (widest diameter in centimeters)
• Anatomic site (specific body region using AMA anatomic terms, with laterality)
• Surgical margin measurement (narrowest margin on each side, in centimeters)
• Total excised diameter calculation (lesion diameter + margin + margin, shown as arithmetic)
• Excision technique (en bloc excision or staged; Mohs surgery is billed under a separate code series)
• Closure method (simple, intermediate, or complex; if intermediate/complex, describe the technique)
• Specimen submission documentation (pathology lab, specimen label, number of specimens)
• Surgeon attestation that the lesion is malignant or consistent with malignancy pending pathology

If the note records the lesion as “approximately 3 cm” without margin arithmetic, the claim cannot be defended as meeting the 11604 threshold. Write the calculation explicitly: “Lesion: 2.7 cm. Margin: 0.2 cm each side. Total excised diameter: 3.1 cm.”

Medicare and payer coverage for CPT code 11604

Medicare covers CPT code 11604 for malignant skin lesion excision when medical necessity is documented. Some Medicare Administrative Contractors (MACs) also publish Local Coverage Determinations (LCDs) on skin lesion removal. Check your region’s LCD and articles before billing.

Prior authorization is not routinely required by Medicare for CPT 11604, though commercial payers may impose their own requirements. Always verify payer-specific authorization rules before scheduling larger excisions, particularly for Medicare Advantage plans, which can differ from traditional Medicare.

CPT code 11604 reimbursement: RVUs, fee schedule, and typical rates

Medicare reimbursement for CPT code 11604 is calculated using the Resource-Based Relative Value Scale (RBRVS). The CMS Physician Fee Schedule publishes annual RVU values and the national conversion factor used to calculate allowed amounts.

The 2026 rates above apply the $33.4009 conversion factor to the national RVUs. RVUs and the conversion factor change every year, so check the FastRVU 2026 RVU lookup or the CMS PFS Look-Up Tool for your locality. Commercial payers’ rates vary widely by contract, often above the Medicare allowed amount.

Practices that bill from a superbill should confirm CPT 11604 maps to the correct fee schedule entry before billing.

Common claim denial reasons for CPT code 11604 and how to avoid them

CPT code 11604 sits on a size threshold, which makes it an easy audit target. Moving a claim from 11603 to 11604 takes only a 1 mm difference in the measurement, so payers look closely. Good denial management catches these errors before the claim reaches the payer.

NCCI edits and modifier rules for CPT code 11604

NCCI edits govern which codes can be billed together on the same claim. For CPT code 11604, the rules that matter most cover same-day excisions and repair codes. CMS updates the edits every quarter, so review the tables on the same schedule.

• Two excision codes, same lesion, same day: Never billable. Billing 11604 with another 11600-11646 excision code for the same lesion on the same date breaks NCCI rules. No modifier can override it.
• Simple repair with 11604: Bundled. No modifier rescues a simple closure code billed with the excision on the same wound.
• Intermediate or complex repair with 11604: Reported separately without modifier 59 when the closure level is documented. Use 59 or an X modifier only when an NCCI edit pairs the codes and the documentation shows a separate, distinct site. XS covers a separate structure and XU an unusual non-overlapping service.
• Modifier 51 (multiple procedures): Apply when billing 11604 with another surgical procedure performed at a separate site on the same day. The lower-valued code receives the reduction.
• Modifier 58 (staged procedure): Applies only to a planned or related staged procedure performed during the postoperative period.

The AAPC Codify CPT lookup shows NCCI edit information alongside each code. Use it to confirm which modifier applies before submission.

How claims management software reduces CPT 11604 denials

Most 11604 denials start before submission, with a missing measurement, an unconfirmed diagnosis, or a payer the patient is no longer covered by. Catching those at the front desk is cheaper than appealing them later.

Pabau, the practice management platform we build, includes claims management software that checks each claim for missing or invalid details before it leaves the practice. In the US, it verifies insurance eligibility through Claim.MD before the visit and submits CMS-1500 claims through the same clearinghouse.

Rejected claims are flagged “Needs action” with the payer’s reason, so your billing team can fix and resubmit them quickly. Payments post straight from electronic remittance advice (ERA) files, matched to the invoice that raised them.

With eligibility, validation, and remittance in one place, an 11604 claim goes out once, with the details a payer checks already attached.

Send cleaner 11604 claims the first time

Pabau checks every claim for missing or invalid details, verifies eligibility, and submits through Claim.MD. Your 11604 claims reach payers ready to adjudicate.

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Conclusion

CPT code 11604 is easy to select and easy to lose. The 3.0 cm lower threshold, the simple-repair bundling rule, and the site exclusions decide most of what goes wrong with it.

Write the lesion size, both margins, and the total into every operative note, and hold the claim until pathology confirms malignancy. Do that, and a 3.1 cm excision bills as 11604 without an argument.

If your team still chases eligibility and rejections by hand, book a demo to see how Pabau gets excision claims out clean the first time.

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