Oncology & Hematology Coding Alert

Question: Our oncologist documented an “excised diameter” of 11 cm by 3.1 cm for a melanoma on the patient’s left leg. This is not the diameter of the lesion itself, it says ‘excised tissue.’ How should we code this?

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Answer: According to the description shared, the best code you can choose for this case is provided as 11604 (Excision, malignant lesion including margins, trunk, arms, or legs; excised diameter 3.1 to 4.0 cm). However, the most precise measurement would be that of the lesion itself plus a notation of the size of the margin needed to completely excise the lesion.

Take the measure before excision: It’s important to measure before excision because the tissue will shrink after excision when the tension on the tissue is released, and will further shrink as it dries and is placed in formalin for preservation.

Add the margin: Your physician should also document the size of the lesion and the smallest surgical margin required to completely excise the lesion, such as 0.1 cm. To get a more satisfactory closure, the skin lesion is usually excised in an elliptical shape, involving far larger margins in two directions than is required to completely excise the lesion. Therefore, as noted in the question, you can’t use the larger margin to select the CPT® code.

Do: Select the CPT® code based on the largest diameter of the lesion, plus two times the smallest required margin. Always count the margin twice because it occurs on both sides of the lesion.

As an example, if the physician noted the malignant lesion of the trunk that measured 3.1 cm plus margins of 0.3 cm to excise completely. The total size of the excision is calculated as 3.1cm + 0.5cm +0.5cm, which equals 4.1 cm. After adding the margins, the correct code is 11606 (…excised diameter over 4.0 cm).

Notice: Your physician could have removed this lesion with the same “excised diameter” as the original example of 11 cm by 3.1 cm, however by not documenting the margins, it is possible the procedure was reported at less of a value then actually performed, but unless documentation supports both the lesion size and margins, it cannot be reported at the larger size. The payment difference would cost your practice $138.70 (based on the 2015 Medicare fee schedule national non-facility amount, conversion factor 35.9335). It is also possible to overbill this procedure as 11604, if the physician had used a long elliptical excision to remove a smaller lesion.

Bottom line: Check the documentation to report the largest lesion diameter and the smallest required margin to most accurately report these services. If documentation is lacking the necessary detail, provide instruction to the physician or clinical practitioner improvement of documentation practices.