Micrographic skin surgery, known as Mohs surgery, is a highly specialized procedure for removing skin cancer while preserving as much healthy tissue as possible. Understanding when to seek diagnostic evaluation and what tests are used can help patients navigate their treatment with confidence.

Introduction: Who Should Undergo Diagnostics and When

Anyone who notices unusual changes in their skin should consider seeking medical evaluation. Mohs surgery is typically recommended after a biopsy—a procedure where a small sample of skin tissue is examined under a microscope—confirms the presence of skin cancer. The most common types of skin cancer treated with this technique include basal cell carcinoma (a slow-growing cancer that rarely spreads but can damage surrounding tissue) and squamous cell carcinoma (a cancer that can spread if left untreated). Less commonly, melanoma and other rare skin cancers may also be treated with this method.^[1][2]

You should consider seeking diagnostic evaluation if you notice a skin lesion that doesn’t heal, continues to bleed, changes in appearance, or grows over time. Particular attention should be paid to areas frequently exposed to the sun, such as the face, ears, nose, lips, hands, and feet. These locations are where skin cancer commonly develops and where Mohs surgery is most beneficial because preserving healthy tissue in these visible areas helps maintain both appearance and function.^[3]

Patients who have had skin cancer previously are at higher risk of developing new cancers and should have regular check-ups with their dermatologist. Those with fair skin, a history of sunburns, extensive sun exposure, or family history of skin cancer may also benefit from routine skin examinations. Early detection through regular self-examinations and professional skin checks can identify suspicious lesions before they become more serious.^[2]

Classic Diagnostic Methods

Initial Skin Examination

The diagnostic process for skin cancer typically begins with a thorough physical examination by a dermatologist. During this examination, the doctor will carefully inspect the suspicious area and surrounding skin. They will look at the size, shape, color, and texture of any unusual spots or growths. The doctor may use a special magnifying instrument called a dermatoscope to examine the lesion more closely and identify features that might indicate cancer.^[5]

Your dermatologist will also ask questions about your medical history, including any previous skin cancers, your family history of skin cancer, your history of sun exposure, and whether you’ve noticed any changes in the lesion. This information helps the doctor assess your overall risk and determine whether further diagnostic testing is necessary. The examination typically includes checking other areas of your body for additional suspicious lesions, as people who develop one skin cancer are at increased risk of developing others.^[12]

Skin Biopsy

If your dermatologist identifies a suspicious lesion during the physical examination, they will perform a biopsy to confirm whether cancer is present. A biopsy involves removing a small sample of the abnormal tissue so it can be examined under a microscope by a pathologist—a doctor who specializes in identifying diseases by studying cells and tissues. This is the definitive way to diagnose skin cancer and determine its type and characteristics.^[1]

The biopsy procedure is usually performed in the dermatologist’s office using local anesthesia to numb the area. There are several types of skin biopsies. A shave biopsy removes the surface layers of skin with a small blade. A punch biopsy uses a circular tool to remove a deeper sample that includes all layers of skin. An excisional biopsy removes the entire lesion along with a small margin of surrounding normal skin. The type of biopsy chosen depends on the size, location, and suspected type of skin cancer.^[5]

After the biopsy sample is taken, it is sent to a laboratory where it is processed and examined microscopically. The pathologist will look for cancer cells and, if present, determine the type of skin cancer, how deeply it has grown into the skin, and whether it shows aggressive features such as perineural invasion (cancer spreading along nerves). This information is crucial for determining the most appropriate treatment approach. The biopsy results typically become available within a few days to a week.^[3][11]

Distinguishing Appropriate Cases for Mohs Surgery

Once skin cancer is confirmed through biopsy, your dermatologist will determine whether Mohs surgery is the most appropriate treatment option. Not all skin cancers require this specialized procedure. Mohs surgery is particularly recommended for skin cancers with a high risk of coming back after treatment or those that have already returned after previous treatment attempts. Tumors that are large, grow quickly, or have edges that are difficult to define visually are also good candidates for this technique.^[1][9]

Location is another important factor in determining whether Mohs surgery is appropriate. Because this technique preserves the maximum amount of healthy tissue, it is especially valuable for cancers located on cosmetically and functionally important areas. These include the face, particularly around the eyes, ears, nose, mouth, and lips, as well as the hands, feet, and genital areas. In these locations, removing extra tissue unnecessarily could affect how you look or how well these body parts function.^[3][11]

Certain microscopic features identified in the biopsy also influence the decision to use Mohs surgery. Cancers with aggressive growth patterns, poorly defined borders under the microscope, or those showing perineural invasion (spreading along nerve pathways) are often treated with this method because it allows the surgeon to track and remove all cancer cells with precision. Skin cancers that have developed in areas previously treated with radiation therapy are also good candidates for Mohs surgery.^[16]

Diagnostics for Clinical Trial Qualification

When patients with skin cancer are considered for enrollment in clinical trials testing new treatments, additional diagnostic procedures may be required beyond the standard biopsy and physical examination. Clinical trials have specific criteria that determine which patients can participate, and these criteria often include detailed diagnostic assessments to ensure the trial is testing the treatment on the appropriate patient population.

For clinical trials involving Mohs surgery or related skin cancer treatments, the diagnostic workup typically includes confirmation of the cancer type through pathological examination. The biopsy results must clearly document the specific type of skin cancer—whether it is basal cell carcinoma, squamous cell carcinoma, or another form. The pathology report may need to include information about the tumor’s characteristics, such as its depth of invasion, growth pattern, and whether it shows high-risk features.^[3][11]

Clinical trials may also require documentation of the tumor’s size, location, and whether it is a new cancer or a recurrence of previously treated cancer. Photographs of the lesion might be taken before treatment to document the baseline appearance. Some trials may require imaging studies such as ultrasound to assess the depth of the tumor or to check whether the cancer has spread to nearby lymph nodes, particularly for more aggressive types of skin cancer.^[4]

Blood tests are not typically used to diagnose skin cancer itself, but clinical trials may require baseline blood work to assess overall health and organ function. This helps researchers ensure that participants are healthy enough to receive the experimental treatment and to monitor for any side effects during the trial. Additional diagnostic procedures may be required depending on the specific focus of the clinical trial and the type of treatment being studied.^[5]

Specialized Surgeon Qualifications

An important aspect of diagnostics related to Mohs surgery involves ensuring that the procedure is performed by appropriately trained specialists. Mohs surgery requires a surgeon who has completed specialized fellowship training beyond standard dermatology residency. These surgeons must be skilled in three distinct roles: as the surgeon who removes the cancerous tissue, as the pathologist who examines the tissue under the microscope, and as the surgeon who reconstructs the wound after cancer removal.^[2][10]

When seeking Mohs surgery, patients should verify that their surgeon is fellowship-trained in this technique and, preferably, board-certified in dermatology. This specialized training ensures that the surgeon has the expertise to accurately interpret the microscopic findings during the procedure and make appropriate decisions about tissue removal. The diagnostic skill of the surgeon during the procedure itself is a critical factor in achieving complete cancer removal while preserving healthy tissue.^[8][13]