Basal Cell Carcinoma (BCC)
Basal cell carcinoma is the most common cancer in humans. It starts in the basal cells. The deepest layer of the outermost layer of skin (the epidermis). BCC grows slowly and almost never spreads (metastasizes) to other organs, which means it is rarely life-threatening. However, if left untreated, it can grow deep into surrounding tissues, including nerves and bone, causing significant damage and disfigurement. Most BCCs appear on areas of the skin that receive regular sun exposure, particularly the face, ears, neck, scalp, and hands.
What BCC Looks Like
BCC can take on several different appearances depending on its subtype. The most common form looks like a pearly or waxy bump. Often with visible blood vessels on its surface and a rolled, shiny border. It may bleed easily after minor trauma, such as washing your face. Some BCCs look like a flat, flesh-colored or brownish scar. Others appear as a pink or reddish patch that may crust, itch, or bleed. If you have a spot that bleeds for no clear reason or heals and then breaks open again, it is important to have your doctor evaluate it.
Helpful Tips
- Look for a pearly, translucent bump with a rolled border on sun-exposed skin.
- A sore that heals, then reopens, or bleeds easily after minor contact should be checked.
- BCC can also appear as a flat white or yellowish scar-like area with poorly defined edges.
BCC Subtypes
Pathologists (doctors who study tissue under a microscope) classify BCC into subtypes based on how the cancer cells are arranged. The subtype matters because some grow more aggressively and are more likely to be incompletely removed with standard surgery.
| Subtype | Appearance | Growth Pattern | Mohs Preferred? |
|---|---|---|---|
| Nodular | Round, pearly, rolled border | Slow, well-defined | Often yes (face/head) |
| Superficial | Pink flat patch, scaly | Slow, surface spread | Sometimes (large or face) |
| Morpheaform / Infiltrative | Scar-like, firm, pale | Aggressive, poorly defined | Yes. High priority |
| Pigmented | Dark brown or blue-black | Similar to nodular | Depends on location |
Causes and Risk Factors
Ultraviolet (UV) radiation from the sun and tanning beds is the main cause of BCC. The damage accumulates over a lifetime, which is why BCC is most common in people over 50. However, anyone can develop BCC, and rates are rising in younger people due to tanning habits. People with fair skin, light eyes, and a history of frequent sunburns are at higher risk. A history of radiation therapy, chronic arsenic exposure, or a weakened immune system (immunosuppression) also increases risk.
Squamous Cell Carcinoma (SCC)
Squamous cell carcinoma is the second most common skin cancer. It arises from squamous cells. The flat cells that make up most of the outer layer of skin. Unlike BCC, SCC carries a meaningful risk of spreading to nearby lymph nodes (the small glands that are part of your immune system) and, in some cases, to distant organs. The overall risk of spread is relatively low for most SCCs (around 2–5%), but this risk rises significantly in people with a weakened immune system, tumors on certain body sites, large or deep tumors, or aggressive subtypes.
Actinic Keratosis: A Warning Sign
Actinic keratosis (AK) is not a skin cancer itself, but it is the most common precancerous skin condition and is considered the earliest step in the development of SCC. AKs appear as rough, scaly patches on sun-damaged skin. Often described as feeling like sandpaper under your fingertip. They are most common on the face, scalp, lips, ears, forearms, and backs of the hands. Left untreated, a small percentage of AKs (roughly 1–5% per year) can progress to invasive SCC. Your doctor will often treat AKs to prevent this progression.
Helpful Tips
- Actinic keratoses feel rough and scaly, like sandpaper on the skin.
- Having multiple AKs significantly increases your lifetime risk of developing SCC.
- Many effective treatments exist, including cryotherapy (freezing), topical creams, and light-based treatments.
Bowen's Disease (SCC In Situ)
Bowen's disease is an early form of SCC sometimes called SCC in situ, meaning 'in place.' This means the cancer cells are confined to the outer layer of skin and have not yet invaded deeper layers. It typically looks like a persistent, slowly growing red or pink scaly patch that can look similar to eczema or psoriasis (a chronic inflammatory skin condition). If Bowen's disease is not treated, it can eventually grow through the skin layer and become invasive SCC, which carries a higher risk of spread.
What SCC Looks Like
SCC most commonly appears as a firm, raised, red bump or nodule on sun-exposed skin. It can also look like a rough, scaly patch, an open sore that does not heal, a growth with a raised edge and a crusted center, or a wart-like growth. SCC of the lip often appears as a persistent scaly or crusted area on the lower lip. SCC can also develop on the mucous membranes inside the mouth or on the genitals. Any non-healing sore or unusual growth that lasts more than a few weeks should be evaluated by your doctor.
Higher-Risk SCC Situations
Most SCCs are treated successfully, but certain features are associated with a higher chance of the cancer returning or spreading. Your doctor will review these factors when recommending a treatment plan. People whose immune systems are suppressed, for example, those who have received an organ transplant (and take anti-rejection medications), have HIV, or are on long-term corticosteroid (steroid) therapy. Are at significantly higher risk for aggressive SCC. These patients should see a dermatologist regularly and have any suspicious lesions evaluated promptly.
Important
- Organ transplant recipients are 65 to 250 times more likely to develop SCC than the general population.
- SCC in people who are immunosuppressed is more likely to be aggressive and should be treated promptly.
- SCC on the lip, ear, temple, or in scars from burns or chronic wounds carries a higher risk of spread.
Other Tumors Treated by Mohs Surgery
While BCC and SCC make up the vast majority of Mohs cases, several rarer skin tumors are also treated with Mohs because of its precise margin control and tissue-sparing properties. Your doctor will discuss which tumors are appropriate candidates for Mohs surgery at your specific clinic.
Dermatofibrosarcoma Protuberans (DFSP)
DFSP is a rare soft-tissue cancer that arises in the deeper layer of skin (the dermis). It grows slowly but has an unusual growth pattern with long, irregular projections of cancer cells that extend far beyond the visible tumor. Making it extremely difficult to remove completely with standard surgery. Mohs surgery is particularly well-suited for DFSP because it can track these irregular projections and remove them completely while sparing surrounding tissue. Recurrence rates with Mohs are significantly lower than with standard wide excision.
Melanoma In Situ and Lentigo Maligna
Melanoma is a cancer of the pigment-producing cells of the skin and is considered more dangerous than BCC or SCC. When melanoma is caught very early. While it is still confined to the outer skin layer. It is called melanoma in situ. Lentigo maligna is a type of melanoma in situ that appears as an irregular tan, brown, or dark patch, most often on the face in older adults. A variation of Mohs surgery called slow Mohs (using a different laboratory preparation method) can be used for lentigo maligna and melanoma in situ, particularly on the face where tissue conservation is important.
Other Rare Indications
Mohs surgery may also be used for Merkel cell carcinoma (a rare and aggressive form of skin cancer arising from touch-sensing cells), sebaceous carcinoma (a tumor of the oil glands, often appearing near the eye), microcystic adnexal carcinoma (a slow-growing but deeply invasive tumor of sweat gland origin), and extramammary Paget's disease (a rare intraepithelial tumor, often in the groin or perianal area). The decision to use Mohs for these tumors is made on a case-by-case basis by a specialist.
Sun Protection: Reducing Your Risk
The most important thing you can do to reduce your risk of skin cancer is to protect your skin from UV radiation. This means applying a broad-spectrum sunscreen with SPF 30 or higher every day, wearing protective clothing (long sleeves, wide-brimmed hats, UV-blocking sunglasses), seeking shade between 10 a.m. and 4 p.m. when the sun is strongest, and avoiding tanning beds completely. If you have had one skin cancer, your risk of developing another one is meaningfully higher. Regular skin checks with your doctor are important for early detection.
Helpful Tips
- Apply sunscreen every morning, even on cloudy days, because UV rays penetrate clouds.
- Reapply sunscreen every two hours when outdoors, or after swimming or sweating.
- Examine your own skin monthly. Look for new or changing spots and report them to your doctor.
- Annual professional skin exams are recommended for anyone with a personal or family history of skin cancer.