Basal cell carcinoma (BCC) is the most common type of skin cancer, accounting for around 80% of all skin cancer cases. It usually develops on sun-exposed areas like the head and neck and can appear as a painless bump or patch on the skin that may bleed and scab over. While basal cell carcinomas are unlikely to spread beyond the original tumor site, some cases can become invasive and penetrate deeper layers of skin. This raises the question – can basal cell carcinoma metastasize (spread) to other parts of the body like the brain?
What is Basal Cell Carcinoma?
Basal cell carcinoma originates in the basal cells located at the bottom layer of the epidermis. These cells produce new skin cells as old ones die off, enabling skin regeneration. When DNA damage from UV radiation triggers abnormal changes in these basal cells, it can cause them to multiply uncontrollably and form a cancerous tumor.
While BCCs often appear on areas frequently exposed to the sun like the head, neck, and back, they can occur anywhere on the body. The major risk factor is excessive UV exposure from the sun or tanning beds. People with lighter skin tones are at greater risk. Basal cell carcinoma most often develops in adults over 40 but can occasionally affect younger people.
The most common locations for basal cell carcinomas include:
- Head – particularly the nose, forehead, scalp, and around the eyes
- Neck
- Shoulders, back, chest
- Arms and hands
- Legs
There are several different subtypes of basal cell carcinoma:
- Nodular BCC – appears as a round, pearly, skin-colored or pink bump.
- Pigmented BCC – appears as a brown, black or blue lesion with dark pigment.
- Superficial BCC – appears as a flat, scaly, reddish patch on the skin.
- Morpheaform or sclerosing BCC – appears as a white, waxy, scar-like lesion.
Can Basal Cell Carcinoma Spread?
Basal cell carcinomas are commonly said to be “non-metastatic” meaning they rarely spread beyond the original site. Most remain localized tumors that do not invade lymph nodes or distant organs when diagnosed and treated early.
However, basal cell carcinoma can sometimes penetrate down into deeper layers of skin and spread to nearby bone or cartilage if left untreated. Basal cell cancers on the head and neck are more likely to become invasive since there are many blood vessels, nerves, and lymph nodes in this area. The estimated metastatic rate is between 0.0028% to 0.55%, meaning spread is very uncommon.
Risk Factors for Spread
While most cases of BCC remain localized, certain high-risk factors can increase the likelihood of metastasis:
- Large tumor size – over 2 cm diameter
- High-risk location – ear, nose, temple, eyelids
- Aggressive histologic subtype – morpheaform, infiltrative, micronodular
- Prior treatment failure and recurrence
- Immunosuppression – organ transplant, HIV/AIDS
- Genetic disorders – basal cell nevus syndrome, xeroderma pigmentosum
If a neglected or recurrent basal cell carcinoma exhibits aggressive characteristics, it has a greater opportunity to penetrate deep into tissues and spread via local invasion or the lymphatic system.
Can BCC Spread to the Brain?
The brain is protected by the blood-brain barrier, making metastasis to the brain extremely rare in basal cell carcinoma. However, a few isolated cases of basal cell carcinoma spreading to the brain have been reported when the primary tumor is highly invasive.
One study looked at 30 patients with metastatic basal cell carcinoma over a 33-year period. Of these 30 cases, only 3 patients had brain metastases – just 10% of those with metastases. The primary tumor location in these cases with spread to the brain included the back/chest wall, nose and neck.
Additional case reports have been published documenting BCC metastasis to the brain, but these account for less than 1% of metastatic basal cell carcinoma tumors. Factors involved in these cases include:
- Tumor neglected for many years before diagnosis
- Large tumor size – often over 5 cm
- Deep invasion into cartilage and bone
- High-risk location like the head/neck
- Aggressive histology – morpheaform or infiltrative subtype
- Recurrence after initial treatment
For a neglected, invasive BCC to metastasize to the brain is very rare but may occur when high-risk prognostic factors are present. catching BCC early and completely removing recurrent tumors helps prevent metastasis.
Signs and Symptoms
In the uncommon event basal cell carcinoma spreads to the brain, the resulting metastases can cause various neurological symptoms such as:
- Headaches
- Nausea/vomiting
- Cognitive changes – memory problems, confusion
- Personality changes
- Seizures
- Vision problems – blurred vision, loss of vision
- Weakness on one side of the body (hemiparesis)
- Difficulty with speech/communication
- Loss of balance/coordination
Since the cerebral hemispheres regulate key functions like movement and cognition, metastases in these areas of the brain can cause corresponding neurological deficits. Basal cell carcinoma spread to the brain can be asymptomatic in early stages but typically becomes symptomatic as tumors grow and disrupt normal brain function.
Diagnosis
If basal cell carcinoma is suspected to have metastasized to the brain, doctors will perform diagnostic imaging tests and possibly a brain biopsy.
Imaging Tests
- MRI – Highly detailed MRI imaging can detect brain tumors and metastases. Contrast enhancement can help differentiate cancer from other abnormalities.
- CT – CT scans provide cross-sectional views of the brain and can identify tumors, bleeds, and skull destruction from cancer.
- PET – A PET scan creates 3D images of metabolic activity and can locate cancer metastases based on increased glucose uptake.
These imaging tests allow identification of any metastatic brain lesions that may be present. The MRI in particular provides clear visualization of the brain anatomy and any lesions.
Biopsy
A small sample of the concerning brain tissue may be extracted through a needle biopsy or surgical procedure. This is examined under the microscope by a pathologist to confirm whether cancer cells are present and if they reflect basal cell carcinoma. Immunohistochemical staining helps identify unique markers seen in basal cell carcinoma.
Treatment
Treatment for basal cell carcinoma that has metastasized to the brain focuses on controlling any symptoms and trying to limit tumor growth through different cancer therapies.
Radiation Therapy
External beam radiation can be directed at brain metastases to damage cancer cells and slow their growth. Stereotactic radiosurgery like Gamma Knife provides targeted radiation treatment to small tumors with minimal damage to surrounding healthy brain tissue.
Surgery
Surgical removal of accessible brain tumors can quickly reduce pressure and swelling in the brain. However, tumors that invade eloquent areas of the brain may not be suitable for resection if it causes significant neurological deficits.
Chemotherapy
Chemotherapy drugs that can cross the blood-brain barrier, such as cisplatin, carboplatin, and etoposide, may be used systemically to combat Basal cell carcinoma that has spread to the brain. Results are often modest compared to traditional chemotherapy responses.
Targeted therapy
Drugs that specifically target molecular pathways and processes in cancer cells have shown some promise against advanced basal cell carcinoma. Options include Hedgehog pathway inhibitors like vismodegib. Responses vary significantly between patients.
Immunotherapy
Immunotherapy stimulates the body’s own immune system to identify and destroy cancer cells. Options include immune checkpoint inhibitors like the PD-1 inhibitors cemiplimab and pembrolizumab. More research is needed regarding responses in brain metastases.
Best Supportive Care
When tumors cannot be controlled through localized or systemic treatments, the goal shifts to palliative care to manage symptoms and maximize quality of life. Corticosteroids help reduce swelling, pain medications treat headaches, and anticonvulsants control seizures.
Prognosis
Basal cell carcinoma metastasis to the brain portends a poor prognosis, but survival times vary depending on multiple factors:
– Number and size of tumors
– Location of tumors
– Patient’s age and overall health
– Effectiveness of treatment
In one review, median survival time after diagnosis of metastatic basal cell carcinoma to the brain was around 7-10 months. However, prognosis is improving with newer therapies like hedgehog inhibitors and immunotherapies. Catching spread early and controlling symptoms remain vital.
Prevention
The best way to prevent spread of basal cell carcinoma to the brain or elsewhere is catching skin cancers early. Primary prevention also involves practicing proper sun protection to avoid excessive UV damage that can lead to development of BCCs:
- Avoid direct sun exposure during peak hours (10am-4pm)
- generously apply broad spectrum sunscreen daily with SPF 30 or higher
- Wear protective clothing – wide-brimmed hats, UV-blocking sunglasses
- Avoid indoor tanning
- Conduct regular self-exams of your skin to identify any new or changing lesions
- Get an annual skin cancer screening with your dermatologist
Prompt diagnosis and treatment of any suspicious growths on the skin are essential to stop abnormal basal cells before they can invade deeper. This protects your overall health.
Conclusion
While it is very rare, basal cell carcinoma does occasionally metastasize to the brain when high-risk features come together like large tumor size, aggressive subtype, and growth near key structures like cartilage. Symptoms of spread to the brain can include headaches, cognitive changes, seizures, and hemiparesis depending on the location affected.
Catching BCCs early, completely removing recurrent tumors, and having regular skin checks are critical preventive steps. New advances in radiation therapy, targeted drugs, and immunotherapy provide hope for controlling rare metastatic basal cell carcinoma. But the prognosis with brain metastases remains guarded, highlighting the importance of primary and secondary prevention.
