Dermatology billing

Biopsies, excisions and repairs

When several biopsies are taken at one visit, only one primary biopsy code is billed: the one with the highest relative value, with the matching add-on code for every other lesion, as the AAFP’s coding guide explains. A biopsy of a lesion you then remove at the same visit is part of the removal, while a biopsy of a different lesion is billed, under the 2026 NCCI policy manual.

Excisions are coded by excised diameter: the greatest clinical diameter of the lesion plus the narrowest margins needed, measured before the excision, according to CGS’s billing article. A 1.2 cm lesion on the back with 0.2 cm margins on each side is 1.6 cm, so 11402 if benign. Benign and malignant codes differ, so the claim waits for the pathology report.

Simple repair is part of the excision. Intermediate and complex repairs are billed on top, except with benign excisions of 0.5 cm or less (11400, 11420, 11440), which include every repair.

Modifier 25, 59 and XS on the same day

A procedure with a 0- or 10-day global period is minor surgery, and the decision to do it is paid inside the procedure, so a same-day E/M takes modifier 25 only when it is significant and separate from that decision.

Modifier 59, or the more specific XS, marks a procedure on a separate lesion or anatomic site. CMS’s modifier guide says to use XS instead of 59 whenever it fits, and never just because two codes are different.

Mohs surgery: stages, blocks and same-day biopsies

Mohs codes belong to the surgeon who removes the tissue and reads the slides, and include the biopsy, excision and pathology. If the slides go to a pathologist, it is not Mohs, and the surgeon bills excision and repair codes. Repairs, flaps and grafts are billed on top.

WPS’s Mohs billing article counts tissue blocks, not slides, puts all added stages on one line with the total units, and uses 17315 for each block past five in any stage. A diagnostic biopsy and frozen section on the Mohs day take 59 when the lesion has not been biopsied in the past 60 days, or the referring physician’s pathology report cannot be obtained with reasonable effort.

Cosmetic or medically necessary

Under CGS’s benign skin lesion policy, removing seborrheic keratoses, cysts, skin tags, nevi or warts is covered only when the note documents a reason such as:

• Bleeding, intense itching or pain
• Recent enlargement, a change in color, or more lesions
• Inflammation or infection, such as oozing or redness
• A lesion that obstructs an orifice or restricts eye function
• Real doubt about the diagnosis, especially possible malignancy

Destruction of actinic keratoses is covered without these limits, and "irritated" alone does not support removal. Removal for appearance is cosmetic: the patient pays and should hear that first. If billed to Medicare at all, it carries GY, or GX after a voluntary notice. Our patient billing team sends those patients a clear statement.

Why dermatology claims deny

Common dermatology denials, with the reason codes that often carry them (codes vary by payer):

• An E/M with modifier 25 that covers only the decision to do the procedure (CO-97)
• A benign lesion removal with no documented reason (CO-50)
• A cosmetic removal sent to Medicare as covered care (CO-96 or PR-96)
• A malignant excision code with a benign or pending diagnosis (CO-11)
• An add-on such as 17003 or 17312 without its primary code (CO-107)

Each one goes through our denial management process, and our denial code guides explain what each code means.

Credentialing for dermatology practices

Each dermatologist, PA and NP billing under their own NPI enrolls with each plan you bill. If your practice reads its own slides or runs a Mohs lab, the lab also needs a CLIA certificate for the testing it does, under 42 CFR 493.3. Our provider credentialing service handles payer enrollment at $189 per payer application, less in bulk.