SCCA stands for squamous cell carcinoma, a cancer that starts in the flat, thin cells lining the surfaces of your skin and many internal organs. It is one of the most common cancers overall, with skin being the most frequent site by a wide margin. The name comes from “squamous” cells, which form the outermost layer of your skin and the interior lining of your mouth, throat, lungs, and other organs.
Where Squamous Cell Carcinoma Develops
Squamous cells cover an enormous amount of surface area in the body, so this cancer can show up in many places. Skin squamous cell carcinoma is the most common form, outnumbering all other locations combined. On the skin, it appears most often on sun-exposed areas: the scalp, backs of the hands, ears, and lips. But it can also develop on the bottoms of the feet, inside the mouth, or on the genitals.
Beyond the skin, squamous cell carcinoma develops in the head and neck region (mouth, tongue, throat, voice box, tonsils, nasal cavity, and sinuses), the lungs, the esophagus, the cervix, the anus, and the bladder. When doctors refer to “SCCA,” they sometimes mean squamous cell carcinoma of the anus specifically, though the abbreviation is also used broadly. The biology is similar across sites: flat surface cells begin growing out of control.
What Causes It
The leading cause depends on where the cancer forms. For skin squamous cell carcinoma, ultraviolet radiation from the sun or tanning beds is the primary driver. UV light damages the DNA in skin cells over time, and the risk compounds with years of exposure. Other factors that raise the likelihood include older age, fair skin, male sex, and a weakened immune system. People who have received organ transplants and take immunosuppressive medications face a notably higher risk.
Human papillomavirus (HPV) plays a major role in squamous cell carcinomas of the cervix, anus, and throat. For these cancers, specific strains of HPV cause the initial cellular changes that lead to uncontrolled growth. Interestingly, a different group of HPV strains (beta-HPVs) may also contribute to skin squamous cell carcinoma, possibly by amplifying UV damage and disrupting the cell’s ability to repair its own DNA. Tobacco use is the dominant risk factor for squamous cell carcinoma of the lungs and a significant contributor to head and neck cancers.
Signs and Symptoms
On the skin, squamous cell carcinoma typically appears as a firm, red nodule or a flat sore with a scaly, crusted surface. It may bleed or develop a rough, wart-like texture. Unlike a pimple or minor irritation, it does not heal on its own. The growth tends to enlarge gradually over weeks to months. Any new or changing skin lesion that persists, especially on sun-exposed areas, warrants attention.
For internal squamous cell carcinomas, symptoms vary by location. In the mouth or throat, you might notice a persistent sore, difficulty swallowing, or a lump in the neck. Lung squamous cell carcinoma can cause a chronic cough, chest pain, or coughing up blood. Cervical and anal cancers may cause bleeding, pain, or changes in bowel or bladder habits. Because these symptoms overlap with many less serious conditions, they often go unnoticed until the cancer has progressed.
How It Is Staged
Staging describes how far the cancer has grown and whether it has spread. Doctors use the TNM system, which evaluates the size of the tumor (T), whether cancer has reached nearby lymph nodes (N), and whether it has metastasized to distant organs (M). For oral cavity squamous cell carcinoma, for example, a T1 tumor is 2 centimeters or smaller with shallow depth, while T3 tumors are larger than 4 centimeters or have grown deeper than 10 millimeters into surrounding tissue. T4 tumors invade nearby bone or other structures.
These T and N categories combine into overall stages from I (small, localized) to IV (advanced or spread to distant sites). The staging system differs slightly depending on the body site. HPV-related throat cancers, for instance, have their own staging criteria because they tend to behave differently and carry a better prognosis than HPV-negative cancers in the same location.
Survival and Prognosis
Prognosis varies enormously based on where the cancer started, how early it was caught, and whether it has spread. Skin squamous cell carcinoma caught early has an excellent outlook, with the vast majority of cases cured through surgery alone. Internal squamous cell carcinomas are more variable. For oral squamous cell carcinoma, five-year survival rates range from roughly 60 to 80 percent for early-stage disease (stages I and II) but drop to about 42 percent for stage III and 19 percent for stage IV.
Cancers found before they reach the lymph nodes are far more treatable. The risk of spread is higher when squamous cell carcinoma involves mucous membranes like the lips, when the tumor is large, or when the patient’s immune system is compromised. This is why early detection matters so much for this type of cancer.
Treatment Options
Surgery is the primary treatment for most squamous cell carcinomas. For skin cancers, there are several approaches. Standard surgical excision removes the tumor along with a margin of healthy tissue. Mohs micrographic surgery is a more precise technique where the surgeon removes tissue layer by layer, examining each one under a microscope during the procedure. This method preserves the most healthy tissue and is often used for cancers on the face, ears, or other cosmetically sensitive areas. Smaller or superficial skin cancers may be treated with curettage (scraping) followed by electrodesiccation (heat treatment), or with cryosurgery (freezing).
Radiation therapy is used when surgery is not practical, either because of the tumor’s location or because a patient cannot tolerate an operation. It may also be used after surgery to reduce the chance of recurrence, particularly for head and neck cancers. Photodynamic therapy and laser treatment are options for certain surface-level lesions.
Immunotherapy for Advanced Cases
For squamous cell carcinomas that have spread or cannot be surgically removed, immunotherapy has become a significant treatment option. These drugs work by helping your immune system recognize and attack cancer cells. Squamous cell carcinomas tend to carry a high number of genetic mutations, which actually makes them more visible to the immune system when given the right boost.
Three immunotherapy drugs targeting the PD-1 protein on immune cells are now FDA-approved for advanced squamous cell carcinoma. Cemiplimab was the first, approved in 2018 specifically for metastatic skin squamous cell carcinoma, with response rates around 47 to 50 percent in clinical trials. Pembrolizumab showed a similar 50 percent response rate in patients with locally advanced or metastatic skin squamous cell carcinoma. Nivolumab is approved for advanced esophageal squamous cell carcinoma and certain head and neck cancers. These treatments do not work for everyone, but they have meaningfully extended survival for patients with cancers that previously had few options.
Prevention and Early Detection
For skin squamous cell carcinoma, the most effective prevention strategy is reducing UV exposure. This means using broad-spectrum sunscreen, wearing protective clothing, seeking shade during peak sun hours, and avoiding tanning beds entirely. The U.S. Preventive Services Task Force specifically recommends UV-reduction counseling for fair-skinned individuals under 25 and selectively for fair-skinned adults over 24 based on their risk factors.
For HPV-related squamous cell carcinomas of the cervix, anus, and throat, HPV vaccination is a powerful preventive tool. Cervical cancer screening through Pap smears and HPV tests catches precancerous changes before they develop into invasive cancer. Avoiding tobacco reduces the risk of squamous cell carcinoma in the lungs, head, and neck.
There is currently no universal screening recommendation for skin cancer in people without symptoms. The USPSTF considers the evidence insufficient to recommend routine full-body skin exams by a clinician for the general population. However, this does not apply to people with a personal or family history of skin cancer, or those who have noticed changes in a mole or skin growth. Regular self-checks, paying attention to new or changing spots, remain one of the most practical ways to catch squamous cell carcinoma early.