Aggressive skin cancers are malignancies characterized by rapid growth and the ability to metastasize. While most skin cancers are highly treatable, aggressive forms can invade deeper tissues and organs. Early detection and intervention are important for successful outcomes.
Types of Aggressive Skin Cancer
Melanoma is an aggressive skin cancer, originating from melanocytes, the pigment-producing cells in the skin. It accounts for a smaller percentage of skin cancer cases but is responsible for a majority of skin cancer-related deaths due to its high potential for spread. Superficial spreading melanoma, the most common type, often appears as a flat or slightly raised discolored patch with irregular borders. Nodular melanoma is a more aggressive form characterized by a raised, often dark-colored bump that grows rapidly. Lentigo maligna melanoma develops in older adults on sun-damaged areas, starting as a flat, mottled tan or brown discoloration.
Squamous cell carcinoma (SCC) develops in the flat, thin cells of the outer skin layer and is the second most common type of skin cancer. While many SCCs are treatable, certain forms exhibit aggressive behavior, particularly those that are large, grow rapidly, or appear on areas of chronic inflammation or immune-compromised individuals. These aggressive SCCs can invade deep into the skin, potentially causing significant damage and disfigurement if not addressed promptly.
Merkel cell carcinoma (MCC) is a rare but aggressive neuroendocrine tumor of the skin, known for its rapid growth and high risk of recurrence and metastasis. It arises from Merkel cells, which are located deep in the top layer of the skin and are connected to nerves. MCC commonly presents as a rapidly enlarging, solitary, firm, red or violet nodule, frequently on sun-exposed areas like the face, neck, or arms. This cancer spreads quickly, often first to nearby lymph nodes and then to distant organs like the brain, bones, or lungs.
Recognizing Warning Signs
For melanoma, the ABCDE mnemonic serves as a guide:
- Asymmetry: One half of the mole does not match the other.
- Border: Irregular, scalloped, or poorly defined edges.
- Color: Varied shades of brown, black, tan, white, red, or blue.
- Diameter: Typically larger than 6 millimeters.
- Evolving: Any noticeable changes in size, shape, color, or texture over time.
This evolution is considered the most important sign.
Aggressive squamous cell carcinomas appear as a firm, red, scaly bump that might bleed or crust over, or as a persistent open sore or wart-like growth. These lesions might also feel sore or tender to the touch. Merkel cell carcinoma presents as a rapidly growing, painless, shiny, or pearly lump, which can be skin-colored, red, purple, or bluish-red. The rapid growth of these dome-shaped or raised tumors is a key indicator. The “ugly duckling” sign, where one mole stands out from others, also warrants inspection.
Factors Influencing Aggressiveness and Prognosis
Beyond the specific type of aggressive skin cancer, several pathological features from a biopsy report influence its aggressiveness and a patient’s prognosis.
Breslow Depth
Breslow depth, or tumor thickness, is a primary determinant for melanoma prognosis. This measurement, taken in millimeters from the skin’s surface to the deepest point of tumor invasion, indicates how far the cancer has penetrated the skin layers. Thinner melanomas, less than 1 millimeter, correlate with a lower chance of spread and a more favorable outlook. Conversely, thicker tumors, especially those greater than 4 millimeters, carry a higher risk of metastasis and a less favorable prognosis.
Tumor Ulceration
Tumor ulceration, a breakdown of the skin surface overlying the melanoma, is another prognostic factor. Melanomas with ulceration are considered more serious because they have an increased risk of spreading, leading to a higher stage classification. The presence of ulceration can reduce the five-year survival rate for melanoma patients. This feature is assessed microscopically and can be categorized by extent, indicating a poorer outlook.
Mitotic Rate
The mitotic rate, or mitotic index, refers to how quickly cancer cells are dividing within the tumor, measured as the number of mitoses per square millimeter. A higher mitotic rate indicates more aggressive cell proliferation and is associated with a lower survival probability. This factor is significant in thinner melanomas and can impact staging and prognosis. A high mitotic rate is an independent predictor of survival.
Pathways to Diagnosis and Staging
The diagnostic pathway for a suspicious skin lesion begins with a visit to a dermatologist. During this initial examination, the doctor visually inspects the lesion and may use a dermatoscope, a handheld magnifying device, for a more detailed view. If the lesion appears concerning, a skin biopsy is performed to obtain tissue for microscopic examination by a pathologist. Common biopsy types include shave biopsy, which removes only the superficial layers; punch biopsy, which extracts a deeper, cylindrical sample; or excisional biopsy, which removes the entire lesion along with a margin of healthy tissue.
Once an aggressive skin cancer is confirmed through biopsy, the next step is staging, a process that determines the extent of the cancer within the body. The American Joint Committee on Cancer (AJCC) uses the TNM system for staging: T for the primary Tumor’s characteristics (size, thickness, ulceration), N for the presence and extent of cancer in regional lymph Nodes, and M for distant Metastasis (spread to other organs). This system helps guide treatment decisions and predict prognosis.
To determine the N stage, a sentinel lymph node biopsy (SLNB) may be recommended. This procedure involves injecting a radioactive tracer and/or a blue dye near the primary tumor to identify the first lymph node(s) to which cancer cells would likely spread. These “sentinel” nodes are then surgically removed and examined for cancer cells. For M staging, imaging scans such as computed tomography (CT), positron emission tomography (PET), or magnetic resonance imaging (MRI) may be used to detect if the cancer has spread to distant organs. These scans provide detailed images of internal structures to identify any secondary tumors.