Basal cell carcinoma (BCC) is a and the most common type of skin cancer overall. BCC is caused by genetic mutations within the sonic hedgehog signaling (SHH) pathway affecting the , hair follicles, and . Important risk factors include UV exposure and a history of organ transplantation. Some individuals have a genetic predisposition to BCC. BCC typically occurs in individuals > 40 years of age and lesions are commonly seen on sun-exposed areas (e.g., head and neck). Typical characteristics include a nonhealing, slow-growing nodule or plaque that may bleed easily or ulcerate. Dermoscopy can be used to support clinical findings, but a skin biopsy is necessary for diagnostic confirmation. Nodular BCC and superficial BCC are the most common histologic subtypes. Risk stratification of BCC is used to classify the lesions as low-risk or high-risk for recurrence after excision and thereby guide management. Tumor resection ( or surgical excision) is the preferred treatment modality; radiotherapy can be considered if resection is not feasible. Other treatment modalities (e.g., cryotherapy, topical pharmacotherapy, photodynamic therapy) may be considered in selected situations but are associated with higher recurrence rates than resection. Metastatic BCC is rare but has a poor prognosis; multidisciplinary care is recommended. All patients should be screened for recurrence and the development of new skin cancers after treatment. Photoprotective measures should be recommended to all individuals for primary prevention and the prevention of recurrent or subsequent skin cancers.
- Intermittent UV exposure is the most significant risk factor, especially for individuals with: 
- Previous history of basal cell carcinoma 
- Presence of any nevus on an extremity 
- Autoimmune conditions (e.g., rheumatoid arthritis) 
- Immunocompromised state (e.g., solid organ transplant recipient)
- Age > 40 years 
- Male sex 
- Exposure to any of the following:
- Genetic predisposition 
The use of a tanning bed before 24 years of age doubles the risk of developing BCC. 
- Nonhealing well-circumscribed pearly papule, nodule, or plaque with rolled borders, telangiectasia, and/or central umbilication (see “Common subtypes of BCC” for further detail)
- Typically located in areas with sun exposure; most commonly on the face and neck
- Advanced lesions often have central ulceration
- Often painless; may be associated with bleeding or pruritus
- Lesions gradually increase in size (indolent growth)
- Perineural invasion can occur in high-risk BCC lesions and manifests as neuropathy.
- Metastasizes rarely (< 1%); can spread to lymph nodes, soft tissue, lungs, and bone
There are several clinical and histological BCC variants; the most common are described here.
BCC lesions may have more than one clinical and histopathological subtype. 
Low-risk BCC subtypes 
Nodular basal cell carcinoma
The most frequently occurring subtype of BCC (accounts for 50–80% of BCC) 
- Papule or nodule with the following: 
- Most commonly located on the face, especially the nose 
Superficial basal cell carcinoma
The second most frequent subtype of BCC (accounts for 10–30% of BCC) 
Plaque with the following:
- Thin and scaly
- Raised border with a pearl-like appearance
- Central atrophy
- Most commonly located on the trunk and legs
Pigmented basal cell carcinoma 
- Nodular or superficial BCC lesion that contain melanin
- Manifests as a blue, brown, or black lesion
- See “Pigmented features of BCC” for further details.
High-risk BCC subtypes 
These lesions account for < 20% of all BCCs.
- Micronodular: erythematous macule, thin papule, or plaque
- Other: basosquamous (metatypical), sclerosing
Nevoid basal-cell carcinoma syndrome (Gorlin syndrome) 
General principles 
- All patients with suspected BCC should undergo a full-body skin examination.
- Dermoscopy can support visual inspection of lesions. 
- A skin biopsy is required for diagnostic confirmation and risk stratification.
- Further evaluation for regional, nodal, or distant metastasis is may be requiredy in patients with high-risk BCC; see “Staging of BCC” for details.
Dermoscopy findings of BCC 
- Arborizing (branching) blood vessels
- Crystalline structures (i.e., shiny white areas or streaks)
Pigmented features of BCC
- Large blue-gray ovoid nests
- Leaf-like structures
- Multiple blue-gray nonaggregated globules
- Spoke wheel-like concentric structures
Skin biopsy 
Select a biopsy technique based on the clinical features of the lesion and procedural risks ; use shared-decision making.
- Ensure adequate sample size and depth (including the deep reticular dermis) for histopathological examination; if not, a repeat biopsy may be required. 
- To optimize the quality of the pathology report, biopsy samples should include the following: 
- Patient demographics
- Presence of risk factors for BCC
- Size and morphology of the lesion
- Initial sample or repeat
Other common skin cancers or precancerous lesions 
Benign skin conditions 
- Definition: a rare, benign tumor of the hair follicle that usually occurs in younger individuals 
- Small annular papule with central depression
- Typically located on the face (e.g., cheek)
- Treatment: Mohs micrographic surgery (especially if on the face) or surgical excision
The differential diagnoses listed here are not exhaustive.
Assessment of disease extent 
- CT with IV contrast: for suspected spread to bone or lymph nodes
- PET-CT or ultrasound: for lymph node metastasis 
- MRI: for suspected perineural or deep soft tissue involvement
- BCC is a locally invasive tumor that rarely metastasizes.
- Staging using the AJCC TNM staging system has limited clinical utility; can be used to stage metastatic disease.
- Stratifying BCC based on the risk of recurrence after excision is recommended to guide clinical decision-making.
Risk stratification of BCC 
Risk stratification is based on clinical and histopathological features.
- High-risk BCC: lesions with any high-risk feature of BCC
- Low-risk BCC: lesions with no high-risk features of BCC
|High-risk features of BCC |
|Tumor characteristics|| |
|Histopathology features|| |
|Patient factors|| |
General principles 
- Definitive treatment of BCC is recommended.
- The choice of therapy is based on:
- Risk of recurrence (see “ ”)
- Need for conservation of tissue and function
- Patient expectations (use shared decision-making)
- Treatment options include:
- Consults and referrals
- Ensure appropriate follow-up for BCC to assess for new or recurrent skin cancers.
Overview of treatment options 
|Overview of treatment options for BCC |
| Mohs micrographic |
| || |
|Surgical excision|| |
|Curettage and |
|Shave removal|| || |
|Radiotherapy (RT)|| |
and/or photodynamic therapy
|Systemic therapies|| |
MMS is considered superior to surgical excision, as the entire tumor margin is intraoperatively assessed to ensure R0 resection, which reduces the risk of recurrence, and the conservation of healthy tissue is maximized. 
BCC typically extends beyond the clinically visible margins. Incompletely excised tumors have a recurrence rate of ∼ 26% compared to ∼ 6% after R0 resection. 
Localized BCC 
- Preferred: MMS
- Surgical excision with wide margins
- RT for patients who cannot undergo resection
- Consider adjuvant RT if there is evidence of perineural or large nerve invasion.
- Preferred: resection
- RT is preferred for patients who cannot undergo resection.
- Alternatives for small, low-risk BCC lesions with no dermal extension in patients who cannot undergo resection or RT
Locally advanced or metastatic BCC 
- Surgery with or without RT (preferred if feasible)
- Hedgehog pathway inhibitors (e.g., vismodegib, sonidegib)
- Immunotherapy with cemiplimab
- Palliative care
- Enrollment into clinical trials
Follow-up for BCC 
Regular follow-up is essential as patients are at an increased of developing subsequent skin cancers. 
- Screen for skin cancers every 6–12 months for 5 years; then annually for life.
- Encourage adherence to photoprotective measures.
- Educate patients and/or caregivers on self-examination to detect recurrence or new lesions.