Basal cell carcinoma (BCC) stands as the most frequently diagnosed form of skin cancer, originating from the basal cells found in the skin’s outermost layer. Typically, these tumors exhibit a slow growth pattern, generally remaining confined to the area where they first appeared. While BCC can manifest in various ways, such as pearly bumps, red patches, or open sores, it commonly develops on sun-exposed skin areas like the face, neck, and ears.
Understanding Metastasis in Basal Cell Carcinoma
While basal cell carcinoma (BCC) is the most common human malignancy, its potential to spread to distant parts of the body, a process known as metastasis, is exceedingly rare. This involves cancer cells breaking away from the original tumor and forming new tumors elsewhere. In the context of BCC, this phenomenon occurs in a very small percentage of cases, with reported incidence rates ranging from approximately 0.0028% to 0.55%.
This low metastatic potential is a defining characteristic that sets BCC apart from more aggressive cancers, such as melanoma. Most BCCs are successfully treated with localized therapies, and the prognosis is generally favorable. Despite its rarity, acknowledging the possibility of metastasis is important, especially when considering certain patient and tumor characteristics that may increase this likelihood. When BCC does metastasize, the secondary tumors are still composed of basal cell carcinoma cells, reflecting their origin.
Factors Influencing Metastatic Risk
Although metastasis from basal cell carcinoma is uncommon, certain factors can elevate the risk when it occurs. The size of the primary tumor plays a role, with larger lesions, particularly those exceeding 2 centimeters or even 4 centimeters in diameter, demonstrating a higher propensity for spread. The anatomical location of the tumor also contributes to risk, with lesions on the head and neck, especially around the eyes, nose, and ears, being associated with increased metastatic potential.
Aggressive histological subtypes, such as morpheaform, infiltrative, or micronodular BCCs, are also recognized risk factors because these types tend to invade deeper into tissues. Additionally, tumors that have recurred multiple times after initial treatment may exhibit more aggressive behavior. Patients with compromised immune systems, whether due to underlying medical conditions or immunosuppressive medications, face an increased risk of developing more aggressive and potentially metastatic forms of BCC.
Recognizing Metastatic Basal Cell Carcinoma
When basal cell carcinoma metastasizes, the cancer cells typically spread to specific locations in the body. The most common initial sites of spread are the regional lymph nodes. Beyond the lymph nodes, in very rare instances, BCC can spread to distant organs such as the lungs, bones, and liver.
The signs and symptoms of metastatic BCC are non-specific and depend on the affected organ. For example, spread to lymph nodes might present as swollen or painful lumps in the neck, armpit, or groin. Lung involvement could lead to a persistent cough or shortness of breath, while bone metastases might cause localized pain.
Treating Metastatic Basal Cell Carcinoma
Managing metastatic basal cell carcinoma typically involves a comprehensive, multidisciplinary approach tailored to the individual patient’s situation. Treatment strategies often include systemic therapies. Radiation therapy may also be used, sometimes after surgery or when surgery is not an option.
Targeted drugs, specifically Hedgehog pathway inhibitors like vismodegib and sonidegib, are a primary treatment for advanced or metastatic BCC. Immunotherapy, which helps the body’s own immune system fight cancer, is another important option, with PD-1 inhibitors like cemiplimab being approved for advanced BCC. Chemotherapy may also be considered in certain circumstances. Due to the rarity and complexity of metastatic BCC, specialized medical expertise is usually involved in its management.