Squamous cell carcinoma (SCC) is a prevalent form of skin cancer, originating in the squamous cells found in the outer layer of the skin. While common, SCC can spread to other parts of the body. This process, called metastasis, occurs when cancer cells break away from the primary tumor and travel to distant sites. When detected and treated early, the prognosis for SCC is generally favorable.
The Nature of Squamous Cell Carcinoma Metastasis
Metastasis describes the process where cancer cells detach from their original tumor and spread to form new tumors in other areas of the body. For squamous cell carcinoma, this begins when malignant cells invade surrounding healthy tissue. These cells then enter the body’s circulatory systems.
Once detached, SCC cells can enter either the lymphatic system or the bloodstream. They commonly travel through lymphatic vessels, part of the immune system, to nearby lymph nodes. From there, they can continue to move through the lymphatic network or potentially enter the bloodstream, reaching more distant organs.
Factors Increasing Metastasis Risk
Several characteristics of the primary squamous cell carcinoma and patient factors can influence the likelihood of metastasis. Larger and deeper tumors carry a higher risk of spreading. Tumors with a diameter greater than 2 centimeters or a depth of invasion exceeding 3.2 millimeters have an increased potential for metastasis.
The tumor’s location also plays a role, with SCCs on areas like the ear, lip, nose, or those arising in scar tissue showing a higher propensity for spread. Aggressive microscopic features, such as poorly differentiated cells or perineural invasion, also increase the metastatic risk. A compromised immune system, often seen in organ transplant recipients or individuals with specific medical conditions, increases the risk of SCC metastasis.
Common Destinations of Spread
When squamous cell carcinoma metastasizes, its initial and most common destination is the regional lymph nodes. These are the lymph nodes located closest to the original tumor site, such as those in the neck for facial SCCs. Approximately 78% of metastatic SCC cases involve lymph node metastasis in draining basins. Monitoring regional lymph nodes is a standard practice due to their frequent involvement.
Beyond regional lymph nodes, distant spread of SCC is less common but can occur. If the cancer travels further, it may reach organs like the lungs, bones, or liver. Distant metastasis is rare, but a serious development.
Recognizing and Addressing Metastasis
Recognizing signs that squamous cell carcinoma may have spread is important for timely intervention. Swollen or tender lymph nodes, new lumps, or unexplained pain in a distant area of the body could indicate metastasis. A physical examination, including palpation of lymph nodes, is typically the first step in detection.
If metastasis is suspected, diagnostic methods such as imaging tests like CT scans or PET scans, along with biopsies of suspicious areas, can help confirm the spread. Managing metastatic SCC often involves a comprehensive approach, combining treatments such as surgery, radiation therapy, and systemic therapies. Systemic therapies, which treat the entire body, may include chemotherapy, targeted therapy, or immunotherapy. These treatments aim to control the disease and improve the patient’s quality of life.