Dermatology Coding Alert

Question: Our dermatologist excised three skin lesions from a patient’s back and neck. I’m trying to figure out what codes to use now that I have the pathology report back. It states, “The largest segment measures 3.5 x 3.5 x 2.0 cm. A second fragment measures 3.0 x 3.0 x 3.0 cm and then in aggregate, the smaller fragments measure 3.5 x 3.0 x 2.0cm.”

Louisiana Subscriber

Answer: You should not code the dermatologist’s skin lesion excision solely from the pathology report. You also need to look at the dermatologist’s record of the procedure. You should determine the appropriate lesion excision size based on the op report, not the pathology report.

Once the specimen is put in the jar and sent to pathology, it shrinks down, sometimes to half its original size. CPT^®’s excision sizes, including margins, are based on the dermatologist’s measurements at the time of the excision. Your dermatologist should always measure an excision prior to cutting and document it with a statement such as, “The lesion measures x cm length by x cm width, which I’m going to excise with an x cm narrowest margin.”

Reminder: Because the margin is applicable to both sides of the lesion, double that measurement. According to CPT^®, the lesion size for coding purposes is based on the largest diameter of the lesion plus the narrowest margin x 2. For instance, taking a 0.5 cm (narrowest) margin on each side of a 3 cm lesion (largest diameter) equals a total of 1 reportable cm plus 3 cm for a total size of 4 cm.

The impact: If your dermatologist doesn’t put the original size in the note, you have to code based on the smaller excision size listed in the pathology report, which could cost your practice over $20 per excision.

Example: The dermatologist’s documentation states that he excised a lesion 1.0 cm length by 2.0 cm width with 0.2 cm margins (code 2.4 cm). The pathology report comes back benign. You would report 11403 (Excision, benign lesion including margins, except skin tag [unless listed elsewhere], trunk, arms or legs; excised diameter 2.1 to 3.0 cm). If, however, the physician had failed to document the size and the pathology report measured a 1.0 cm lesion plus 0.1 margins, you could code only 11402 (…excised diameter 1.1 to 2.0 cm), resulting in a loss of $25.86 (non-facility national amount, conversion factor 34.023: 11403 = $195.63 minus 11402 = $169.77 — difference $25.86).

Important: You do need the pathology report to choose a code, but not for the size of the excision. You should always choose the malignant or benign excision code based on the results of the pathology report, even if the dermatologist did not know at the excision time that the lesion was malignant. The pathology report offers the definitive diagnosis that serves as the basis for the CPT^® excision code selection.