General Surgery Coding Alert

Question: I am confused regarding how to determine lesion size when coding for excisions. For instance, if the surgeon excises a malignant 5-mm, right lateral chest lesion with margins of 7 mm x 17 mm, what is the appropriate code?

South Dakota subscriber

Answer: Your surgeon will often make elliptical excisions in an attempt to bring the skin together more easily during suture and "flatten" or minimize the resulting scars. If you imagine a long, thin scar, for instance, you can see how this would be less noticeable -- especially over time -- than a more rounded "hole" that the physician cannot suture or close neatly. You can see an illustration of an excision of this type on page 54 of the 2008 AMA Professional Edition of the CPT Manual.

You should not let the elliptical, uneven margins confuse you, however. The total amount of skin surface the surgeon removes does not determine the excision code you select.

Rather, under CPT coding instructions, you would determine the correct code by measuring the lesion at its widest point, before excision, and adding to it twice the measurement of the smallest margin (again, before excision).

In a nutshell: You should always use the smallest, not the largest, margin when figuring your final code choice.

So, for instance, for a right lateral chest lesion measuring 0.5 cm and with margins 0.7 x 1.7 cm, you would add 0.5 cm (the lesion's size) to the smallest margin (0.7 cm) multiplied by 2. (CPT descriptors stipulate measurements in centimeters. Because your surgeon documented millimeters in this case, simply move the decimal point one place.) The total measurement would equal 1.9 cm (0.5 + [0.7 x 2]).

For a malignant lesion, the correct code is 11602 (Excision, malignant lesion including margins, trunk, arms or legs; excised diameter 1.1 to 2.0 cm).