Mohs Micrographic Surgery is a highly specialized procedure used to treat common forms of skin cancer, such as basal cell carcinoma and squamous cell carcinoma, by precisely removing cancer layer by layer while sparing healthy tissue. Medicare covers Mohs surgery when a physician determines the procedure is medically necessary for treating skin cancer. This coverage is generally robust, but the specific financial details and approval process require understanding the program’s rules.
Coverage Under Original Medicare
Original Medicare, consisting of Part A and Part B, covers Mohs surgery as an outpatient service under Part B. Since the procedure is typically performed in a dermatologist’s office or an ambulatory surgical center, Part B coverage includes the surgical excision, the immediate microscopic examination of the tissue to confirm clear margins, and any medically necessary wound reconstruction.
For coverage to apply, the procedure must be performed by a Medicare-enrolled provider in a Medicare-approved facility. When a provider agrees to “accept assignment,” they accept the Medicare-approved amount as full payment. This acceptance helps determine the final cost to the beneficiary and prevents unexpected balance billing.
Defining Medical Necessity for Procedure Approval
Coverage is not automatic for every skin cancer diagnosis and hinges entirely on the concept of medical necessity as defined by Medicare. The physician must document why Mohs surgery, rather than a standard excision, is the most appropriate treatment for the specific tumor. Justification is often based on tumor characteristics and anatomical location that carry a higher risk of recurrence or require maximal tissue preservation.
Tumors located in cosmetically or functionally sensitive areas—such as the face, ears, nose, lips, scalp, hands, feet, or genitals—frequently meet the criteria for medical necessity. Necessity is also established for tumors that are large, have poorly defined borders, or are of an aggressive subtype, like an infiltrative basal cell carcinoma. Medicare requires that the same physician perform both the surgical removal and the immediate pathological examination of the tissue. Claims that do not meet these strict documentation requirements may be denied, shifting financial responsibility to the patient.
Understanding Patient Cost Responsibility
Once the Mohs procedure is approved as medically necessary under Original Medicare Part B, the beneficiary is responsible for a portion of the total cost. The first financial step is meeting the annual Medicare Part B deductible. After the deductible is satisfied, Medicare Part B covers 80% of the Medicare-approved amount for the procedure and related services.
The remaining 20% of the approved amount is the patient’s coinsurance responsibility. Since Mohs surgery can involve multiple stages and complex reconstruction, the 20% coinsurance can be a significant out-of-pocket expense. Patient costs are minimized when the provider accepts assignment, preventing them from billing the patient above the Medicare-approved rate. Beneficiaries should confirm this status before the procedure.
Impact of Medicare Advantage and Supplemental Plans
Beneficiaries enrolled in a Medicare Advantage Plan (Part C) receive their coverage through a private insurance company, but these plans are required to cover all the same services as Original Medicare. However, the way a Medicare Advantage plan structures patient costs can differ substantially from the Part B model. These plans may substitute the 20% coinsurance with fixed copayments, which could be lower or higher, and often impose a maximum out-of-pocket limit.
Medicare Advantage plans frequently operate with provider networks and may require a referral from a primary care physician or a prior authorization for the Mohs procedure. Failing to adhere to the plan’s specific network or authorization rules may result in a higher cost or a complete denial of the claim.
Separately, beneficiaries with a Medicare Supplement Insurance policy, commonly known as Medigap, use these plans to fill the financial gaps left by Original Medicare. Medigap policies are designed to cover the patient’s 20% Part B coinsurance and often the annual deductible, which significantly reduces the beneficiary’s out-of-pocket spending for the entire Mohs procedure.