Dermatology Coding Alert

Unnecessarily modifying surgery can knock $130 from your reimbursement

A dermatologist in your practice removes a cancerous lesion in horizontal sections and sends the tissue to pathology for analysis. If you would code this procedure as Mohs surgery, you're putting your practice at risk for fraud charges.

Mohs surgery is regarded as one of the most effective treatments for skin cancer. But successful coding for Mohs procedures involves knowing how to report each stage, when and when not to modify the code, and, especially, when you're allowed to use the codes in the first place. Let the answers to these frequently asked questions guide you to ethical and profitable Mohs coding.

Q: When is it appropriate to use the Mohs codes?

A: The Mohs chemosurgery codes (17304-17310, Chemosurgery [Mohs micrographic technique], including removal of all gross tumor, surgical excision of tissue specimens, mapping, color coding of specimens, microscopic examination of specimens by the surgeon, and complete histopathologic preparation including the first routine stain ...) are unique because they are "the only CPT codes that describe procedures that involve surgery and pathology services performed together by the same surgeon or pathologist," the 2004 CPT Assistant states.

In Mohs surgery, "the physician works as a surgeon and a pathologist," says Margarida Cabral, CPC, coder for the dermatology department of the Lahey Clinic in Burlington, Mass. Report these codes only if the dermatologist performs both the excision of the tissue and examines the excised tissue to locate remaining tumors, she says. If a separate pathologist is involved, you should report the dermatologist's and pathologist's services with separate codes.

Example: The dermatologist removes a cancerous area 0.8 cm in diameter, and then excises one layer of the excised tumor. He sends the specimen to a pathologist, who fresh-freezes the tissue and examines the margins microscopically, marking the location of any remaining tumor on the map of the surgical wound. In this case, the dermatologist did not perform the full Mohs procedure. Report the dermatologist's work with 11641 (Excision, malignant lesion including margins, face, ears, eyelids, nose, lips; excised diameter 0.6 to 1.0 cm).

Q: Do I need to append modifier 51 if the dermatologist performs more than one stage of Mohs?

A: Depending on what he finds in the margins of the first stage of the tumor, the dermatologist may have to excise more tissue to remove any remaining cancer. Many times, when a physician performs multiple procedures, he does not need to repeat all of the work for the second and subsequent procedures. Modifier 51 (Multiple procedures) recognizes this fact by lowering the reimbursement for subsequent procedures to reflect the fact that less work was performed.

But this is not the case with Mohs surgery, Cabral says. CPT recognizes that "greater than 80 percent of the work is intraservice work that does not overlap when two or more procedures are performed," the CPT Assistant says. The Mohs procedures are exempt from the reimbursement-lowering effects of modifier 51.

Example: The dermatologist excises one layer of a tumor on a patient's cheek, examines it, and returns to excise another layer to remove the remaining cancer. Report 17304 (... first stage, fresh tissue technique, up to 5 specimens) and 17305 (... second stage, fixed or fresh tissue, up to 5 specimens) without appending modifier 51.

Helpful: Many CPT manuals mark modifier 51-exempt codes with a "X" symbol.

Q: What if the dermatologist performs more than three stages?

A: To pick the correct Mohs surgery codes, you need to know two things: