First you need to convert the mm's to cm's as CPT codes for lesions are in cm's. So 3mm converts to 0.3 cms. Your margin is 0.3 cm.
So, now your question becomes:
A surgeon documents a malignant lesion 2 cm X 3.2 cm with 0.3 cm margins is excised from the shin with complex repair. How do we figure out the size for the multi-dimensional lesion plus the margins for CPT coding?
I got out my Blitz and watched Laureen explain how to figure the dimension of a lesion and its margins and select the appropriate code from the correct "location, location, location" bubble. (I love how Laureen emphasizes things like that.
If you don't already have it, try to invest in the Blitz DVD's or online version.)
So, in the Blitz, Laureen explains, if it is a lesion having multiple dimensions, take the diameter (the largest side of the lesion) and add that to the margin twice because the margins would be at both ends of the lesion . So, in your question above, that would be the 3.2 cm (the diameter) added to 0.3 cm (the margin) twice. That gives you 3.8. (3.2 cm + 0.3 cm + 0.3 cm = 3.8 cm)
(
Another way to do it is to take the margin, 0.3 cm, and multiply it by two, because it is at both ends of the lesion. So that would be 0.6 cm. Then add that to the diameter of the lesion, the 3.2 cm. That gives you 3.8 cm....just another way that gets the same correct result.)
So then you would find the code for the correct location that includes 3.8 in it's size range. The correct code for this lesion would be 11604. And then you would also need to code the complex repair if documented as complex repair.
Hoping that helps some.
