Here's a copy of an AAPC article by John Verhovshek regarding your question. See the 3rd or 4th paragraph down starting with 'To assign a malignant lesion CPT code...' This article captures some really good points.
Hope this helps.
Skin Lesion Excisions
By John Verhovshek
In CMS
October 1, 2013
Skin Lesion Excisions
Three answers in the report will help you piece together the coding puzzle.
To accurately code for excision of a skin lesion, you need to be able to extract from the documentation the answers to three very important questions:
Was the lesion benign or malignant?
Where was the lesion located (anatomic site)?
What was the excised diameter of the lesion?
Let’s examine how these parameters are determined, and how they affect your code selection.
Determine Classification
Excision codes fall into two main classifications: Those describing benign (non-cancerous) lesions and those describing malignant (cancerous) lesions.
Per ICD-9-CM Official Guidelines for Coding and Reporting (chapter 2: Neoplasms), “To properly code a neoplasm it is necessary to determine from the record [e.g., pathology report] if the neoplasm is benign, in-situ, malignant, or of uncertain histologic behavior.”
If the pathology report describes a benign lesion, or one of uncertain behavior (e.g., indications of atypia or dysplasia), you must use a benign lesion CPT® code (11400-11446).
To assign a malignant lesion CPT® code (11600-11646), the pathology report must confirm a malignancy, which may be primary (malignancy at the site where a cancer begins to grow), secondary (malignancy has spread from the primary site to other parts of the body), or in-situ (an early-stage tumor that may evolve into an invasive malignancy).
Be certain that your code selection is backed up by the pathology report, even if that means holding the claim for a few days. If you don’t have a pathology report to confirm the diagnosis, you must assign an unspecified diagnosis and a benign lesion excision CPT® code (11400-11471). The only legitimate exception to this rule is if the provider performs a re-excision to obtain clear margins at a later operative session. In such a case, report the same diagnosis as that used for the initial procedure.
Determine Location
Report each lesion excision independently, using the following site-specific classifications:
Benign lesion
Trunk, arms, legs – 11400-11406
Scalp, neck, hands feet, genitalia – 11420-11426
Face, ears, eyelids, nose, lips, mucous membrane – 11440-11446
Malignant lesion
Trunk, arms, legs – 11600-11606
Scalp, neck, hands, feet, genitalia – 11620-11626
Face, ears, eyelids (skin only), nose, lips – 11640-11646
Determine Size
Size is of primary importance when reporting lesion excision. Per CPT®, “Code selection is determined by measuring the greatest clinical diameter of the apparent lesion plus that margin required for complete excision.” The margin is further defined as “the most narrow margin required to adequately excise the lesion ….”
In plain language, the excised diameter equals the length of the lesion at its longest point, plus two times the narrowest margin. For example, if the lesion measures 1 cm at its greatest, and the surgeon removes a margin of 0.5 cm on all sides, the total excised diameter is 2.0 cm (1.0 cm + [2 x 0.5 cm]).
Your physician should measure the lesion plus margin before the excision. Do not select codes based on the size of the incision and/or the resulting surgical wound.
Put It All Together and Code It
When you have the facts—classification, location, and size—you are ready to code the service. Here are a few examples of how you might use the information to determine proper coding.
Example 1: A surgeon excises a malignant lesion from a patient’s right shoulder. Prior to excision, the lesion measures 1.0 cm at its widest. To ensure removal of all malignancy, the surgeon allows a margin of at least 1.0 cm on all sides, for a total excised diameter of 3.0 cm (1.0 cm + [2 x 1.0 cm]).
The correct code is 11603 Excision, malignant lesion including margins, trunk, arms, or legs; excised diameter 2.1 to 3.0 cm.
Example 2: The surgeon removes a single lesion from the left cheek. The lesion measures 1.5 cm at its widest, around which the surgeon removes a margin of 0.5 cm. The pathology report reveals a neoplasm of uncertain behavior.
“Uncertain behavior” requires you to report benign lesion excision (11400-11446). The location is the cheek, which narrows your choice to codes 11440-11446. The total excised diameter is 1.5 cm (the lesion itself) plus twice the margin (2 x 0.5 cm = 1.0 cm), or 2.5 cm.
The correct code is 11443 Excision, other benign lesion including margins, except skin tag (unless listed elsewhere), face, ears, eyelids, nose, lips, mucous membrane; excised diameter 2.1 to 3.0 cm.
Multiple Excisions Require a Modifier
Treat each lesion excision as an individual and separate procedure, and link a verifiable diagnosis to each individual CPT® code for multiple excisions. Append modifier 59 Distinct procedural service to the second and subsequent codes describing excisions at the same location to avoid duplication denials.
Example 3: The surgeon removes three lesions from the left arm, with total excised diameters of 0.5 cm (benign), 1.5 cm (benign), and 2.0 cm (malignant). Proper procedure and diagnosis coding is:
11602 Excision, malignant lesion including margins, trunk, arms or legs; excised diameter 1.1 to 2.0 cm with 173.6 Other malignant neoplasm of skin, skin of upper limb, including shoulder
11402-59 Excision, benign lesion including margins, except skin tag (unless listed elsewhere), trunk, arms or legs; excised diameter 1.1 to 2.0 cm with 216.6 Benign neoplasm of skin; skin of upper limb, including shoulder
11400-59 Excision, benign lesion including margins, except skin tag (unless listed elsewhere), trunk, arms or legs; excised diameter 0.5 cm or less with 216.6.
“Re-excision” Calls for Special Consideration
The physician may revisit a previous excision to remove additional material if pathology continues to show malignancy in the margins. How you report this depends on the timing of the follow-up excision.
If the re-excision occurs during the same session as the initial excision, report a single code to describe the greatest area removed. For example, if the first excision measures 3.0 cm with margins, and the second excision increases the margins by 1.0 cm on all sides, code for a 5.0 cm excision. Do not separately report a 3.0 cm excision and a 5.0 cm excision.
If the re-excision occurs during a subsequent session, however, base your code selection on the diameter of the new excision. For example, you report 11603 Excision, malignant lesion including margins, trunk, arms or legs; excised diameter 2.1 to 3.0 cm for the initial excision on Tuesday. Pathology indicates inadequate margins to remove all malignancy. The physician returns the patient to the procedure room three days later (Friday) and increases the margin by 1 cm on all sides. You report Friday’s session using 11606 Excision, malignant lesion including margins, trunk, arms or legs; excised diameter over 4.0 cm, with modifier 58 Staged or related procedure or service by the same physician during the postoperative period appended because the re-excision occurred during the global period of the initial excision.
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Excision Differs From Shaving, Destruction
In addition to the skin lesion excision codes (11400-11646), CPT® also includes codes to describe lesion removal by shaving (11300-11313), destruction (17000-17004), and paring or cutting (11055-11057). A few simple definitions distinguish between these various procedures.
CPT® defines excision as “full-thickness (through the dermis) removal of a lesion including margins …” An excision is performed with a scalpel held perpendicular to the skin, and involves cutting into the subcutaneous tissue to remove the entire lesion.
By contrast, CPT® defines shaving as “The sharp removal by transverse incision or horizontal slicing to remove epidermal and dermal lesions without a full thickness dermal excision.” In other words, the physician uses a scalpel, placed horizontally to the patient’s skin, to slice off a piece of the lesion.
Paring or cutting describes the removal of superficial tissue using a spoon-shaped surgical instrument called a curette (credit armondo). This procedure is also called curettement.
Lesion destruction occurs via laser surgery, electrosurgery, or other methods (but not a scalpel). Always expect a diagnosis of 702.0 Actinic keratosis with the premalignant lesion destruction codes (17000-17004).
Lesion Excision Bundling Concerns
When reporting excision of skin lesions (11400-11646), in addition to other procedures at the same anatomic location during the same session, be on the lookout for the following bundling issues.
Do not report in addition to lesion excision:
Local anesthesia
Simple closures (12001-12018)
Report in addition to lesion excision:
Intermediate (12031-12057) and complex (13100-13153) repairs
Reconstructive closure (15002-15261, 15570-15770)
Do not report lesion excision in addition to:
Adjacent tissue transfer (14000-14350)
G.J. Verhovshek, MA, CPC, is managing editor at AAPC