Dermatology Coding Alert

What would you do in these clinical scenarios?

Mohs is a treatment procedure for a patient with diagnosed skin cancer. As opposed to a “wide excision,” the goal of Mohs is to remove the entire lesion (ensure clear margins) while preserving healthy tissue, as much as possible. To accomplish this, the physician excises the lesion, then performs histology to ensure clear margins while the patient is still in surgery. The first excision of a single lesion is the first “stage.” 

The physician will take the tissue from the first stage, map and divide the tumor into pieces, and embed each piece of tumor into an individual mounting medium, such as frozen blocks. Each of these pieces of separately embedded tissue from a single stage is a “block,” and the physician typically prepares a few blocks from a single stage.

Whether the physician continues to a second stage depends on the histologic findings. If the margins are clear, the procedure is complete. On the other hand, if the physician finds tumor cells in the margins of any of the tissue blocks, he will go back and remove more tissue from the patient during the same operative session. Each time the physician excises more tissue from the same, you have another “stage” in the Mohs procedure.

Take a look at these Mohs coding scenarios, and check your skills against our expert answers later in this issue.

Question 1: The patient presents with a basal cell carcinoma of the central portion of the forehead. The dermatologist removes the carcinoma (first stage) and divides it into four tissue blocks for examination. Upon microscopic examination, the physician finds the margins are clear of carcinoma. What CPT® code(s) would you report for this procedure?

A: 1 unit of 17311

B: 4 units of 17311

C: 1 unit of 17311, 1 unit of 17312

D: 1 unit of 17311, 1 unit of 17315

Question 2: The patient presents with a squamous cell carcinoma of the nose. The dermatologist removes the carcinoma (first stage) and divides the stage into six tissue blocks. He examines the samples and finds that the margins are not clear. So he removes the positive margin with another excision (second stage), dividing it into three tissue blocks for examination. Those margins prove to be negative (clear). What CPT® code(s) would you report for this procedure?

A: 1 unit of 17311

B: 1 unit of 17311, 1 unit of 17312

C: 1 unit of 17311, 8 units of 17312

D: 1 unit of 17311, 1 unit of 17312, 1 unit of 17315

Question 3: A patient presented to the physician with a diagnosis of primary squamous cell carcinoma on the vermilion border of his lower lip. The dermatologist planned a layered excision of the lesion to preserve the integrity of the healthy skin surrounding the neoplasm. The practice has arrangements with a nearby hospital to provide the pathology needed. After the dermatologist removed tissue, the 1.8 cm excision was taken to the hospital, and after three days the pathology report showed the tissue sample was malignant. During the follow-up session on another day, the dermatologist proceeded with two more stages of lesion excision (comprising margins of 2.1 cm and 2.4 cm) during the same session. It wasn’t until the 2.4 cm excision that the hospital’s pathologist was able to report no sign of cancer. What CPT® code(s) would you report for this encounter?

A: 1 unit of 17311

B: 3 units of 17311

C: 1 unit of 17311, 2 units of 17312

D: 1 unit of 11642, 1 unit of 11643

Question 4: A dermatologist encounters a patient for reconstruction after the patient has received Mohs from another physician. He repairs a 2.4-cm defect using two advancement flaps. Would you use the Mohs CPT® codes for this procedure?