Dermatology Coding Alert

Question: I've been getting conflicting advice on coding lesion excisions. I heard that I should use the size of the excision before it goes to pathology, but then a consultant said that we should wait until after the pathology so we can code the diagnosis accurately. Which is right?


New Mexico Subscriber

Answer: Both are right--partially. Since the lesion excision codes (11400-11646) are size-based, you need the size of the lesion before the dermatologist removes it. The lesion will become smaller as soon as it's free from the tension of the surrounding skin, and it will probably shrink further when placed in formaldehyde for pathology. But you also need to wait for the pathology report for the correct diagnosis.

Example: The dermatologist excises an irregularly shaped lesion from just below the patient's right shoulder. The lesion measures 2 cm at its widest. The surgeon allows a margin of at least 1.5 cm on all sides.

To calculate the excised diameter, you should begin with the size of the lesion (2 cm) and add the width of the narrowest margin multiplied by 2 (1.5 x 2, or 3 cm total) for a total of 5 cm (2 + 3 = 5).

But because CPT classifies lesions as either "benign" or "malignant," you should always wait for the pathology report before selecting ICD-9 or CPT codes.

Example: Pathology confirms that the lesion in the above example is a primary malignancy. In this case, therefore, you should report 11606 (Excision, malignant lesion including margins, trunk, arms or legs; excised diameter over 4.0 cm).

To find a diagnosis, go first to the table of neoplasms and look for "neoplasm of the skin, shoulder." When you find this entry, follow the column marked "primary" to arrive at a provisional diagnosis of 173.6. Checking the tabular listing confirms that this diagnosis applies to "Other malignant neoplasm of skin; skin of upper limb, including shoulder."