Squamous cell carcinoma (SCC) is the second most common type of skin cancer, with an estimated 1.8 million cases diagnosed in the United States each year. It arises from the abnormal growth of squamous cells, which make up the outermost layers of the skin. While it is a form of cancer, it is highly treatable, particularly when identified in its early stages. Understanding the nature of this condition is a first step toward recognizing its signs and seeking timely evaluation.
Understanding Invasive Squamous Cell Carcinoma
To understand what makes squamous cell carcinoma “invasive,” it helps to know the skin’s basic structure. The skin has two main layers: the epidermis on the outside and the dermis beneath it. Squamous cells are flat cells located in the upper part of the epidermis. When these cells become cancerous but remain confined to this top layer, the condition is called squamous cell carcinoma in situ, or Bowen disease.
The term “invasive” signifies the cancer has progressed beyond its point of origin. In invasive squamous cell carcinoma, the cancerous cells have broken through the base of the epidermis and grown into the deeper dermis layer. This progression is a step beyond the in situ stage.
Once the cancer becomes invasive, it can grow further into underlying tissues, lymph nodes, and even bones if left untreated. The distinction between in situ and invasive SCC is important, as it determines the cancer’s stage and influences treatment. Invasion into the dermis gives the cancer access to blood vessels and lymphatic channels, which can facilitate its spread to other parts of the body.
Risk Factors and Prevention
The primary cause of squamous cell carcinoma is DNA damage within skin cells, which results from prolonged exposure to ultraviolet (UV) radiation. This exposure can come from the sun or artificial sources like tanning beds. About 90 percent of nonmelanoma skin cancers are associated with UV radiation exposure.
Certain individuals are more susceptible to developing SCC. Those with fair skin, light-colored eyes, and blond or red hair have less melanin, a pigment that provides some natural protection from the sun. A weakened immune system, from a medical condition like HIV or immunosuppressive drugs, also increases risk; organ transplant recipients are about 100 times more likely to develop SCC. Other factors include a personal history of skin cancer, chronic skin inflammation from scars or burns, and exposure to the human papillomavirus (HPV).
Preventing SCC involves protecting the skin from UV light. This includes wearing protective clothing, wide-brimmed hats, and sunglasses, as well as applying a broad-spectrum sunscreen with an SPF of 30 or higher. Sunscreen should be applied 30 minutes before going outdoors and reapplied every two hours. Avoiding tanning beds, limiting alcohol consumption, and not smoking are other effective preventive measures.
Identification and Symptoms
Invasive squamous cell carcinoma most commonly appears on sun-exposed areas of the body, such as the face, ears, neck, scalp, lips, and the backs of hands, but it can develop anywhere. The appearance of SCC can vary, but there are several common presentations.
One frequent sign is a persistent, scaly red patch of skin that may have irregular borders and can sometimes crust or bleed. Another is a firm, raised growth or nodule, which might have a depression in the center. SCC can also present as an open sore that heals and then reopens, or it can look like a wart-like growth.
On the lips, it may appear as a persistent sore or an area that is pale, dry, and cracked. A lesion may feel tender or painful as it grows. The persistent and changing nature of these spots is an important indicator. Any new or changing skin lesion, or a sore that does not heal within a couple of months, should be evaluated by a doctor.
The Diagnostic Process
The diagnostic process for invasive squamous cell carcinoma begins with a clinical examination. A doctor or dermatologist will assess any suspicious growths, noting their size, shape, color, and texture, and will ask about your medical history, including sun exposure and family history of skin cancer.
While a physical exam can raise suspicion, a diagnosis is confirmed with a skin biopsy. This procedure involves removing a small sample of the suspicious tissue for laboratory examination. The type of biopsy used depends on the lesion’s size and location. Common types include a shave biopsy, a punch biopsy for a deeper sample, or an excisional biopsy to remove the entire growth.
A pathologist examines the tissue sample under a microscope. This analysis confirms whether cancer cells are present and determines if the cells have invaded the dermis, which establishes if the cancer is in situ or invasive. The pathologist’s report provides details on the cancer’s depth and other features, which helps in staging the cancer and guiding the treatment plan.
Treatment Modalities
The treatment for invasive squamous cell carcinoma aims to completely remove the cancerous tumor. Surgical removal is the primary approach, with the choice of technique depending on the tumor’s size, location, and depth, as well as the patient’s overall health.
Excisional Surgery
This is a standard treatment where a surgeon removes the tumor using a scalpel, along with a surrounding margin of healthy skin. This margin helps ensure all cancerous cells are removed. The tissue is then sent to a laboratory to confirm that the margins are clear of cancer. This procedure is often used for small, early-stage SCCs and has a high cure rate.
Mohs Micrographic Surgery
For tumors in sensitive or functionally important areas like the face, ears, or hands, Mohs surgery is often recommended. In this precise procedure, the surgeon removes the visible tumor and then removes surrounding skin one thin layer at a time. Each layer is immediately examined under a microscope until no cancer cells are detected, which spares the maximum amount of healthy tissue.
Other Treatments
Other treatments are available for specific situations. Curettage and electrodessication involves scraping away the tumor with a curette and then using an electric needle to destroy any remaining cancer cells; this method is used for smaller, superficial tumors. Radiation therapy may be used for patients who are not suitable for surgery or for very large tumors, sometimes as an additional treatment after surgery.