Overview

Our lips are a central part of the body, both in terms of our appearance and in daily functions, such as eating and swallowing. However, the lips are more sensitive than one would think, as they are the most exposed area to the sun, making them a vulnerable site for a type of oral cancer, such as lip cancer.¹ 

The regions of the lips most susceptible to cancer are: the external skin above the lips, the vermilion border (the pink transitional area from the skin), internal mucosa (lining inside the lips), and the corners of the mouth.² The lips are thin and lack a thick layer of melanin, which provides protection from ultraviolet radiation (UV). This makes the lower lip especially susceptible to sun damage, a key risk factor for developing skin cancer.² 

Additionally, exposure to some environmental factors like use of tobacco, alcohol consumption, human papillomavirus (HPV), and previous hematopoietic stem cell transplant are factors that make an individual more prone to chronic irritation and cellular damage.¹ 

Lip cancer is a concerning disease with a frequency of 1-2% accounting for 23-30% of oral cancers, most commonly found in older male fair-skinned adults and individuals under prolonged sun exposure with outdoor occupations.³ 

The risk of mutations leading to cancerous growth increases due to the high turnover rate of the mouth lining.⁴ Among the various types of lip cancer, two of the most common are squamous cell carcinomas (SCCs) and basal cell carcinomas (BCCs).⁵ They are forms of non-melanoma skin cancer that can develop on or around the lips. 

However, while they may appear similar, these two cancers differ greatly starting from their origin, behaviour, and presentation. Understanding the distinction between SCCs and BCCs is more than a matter of medical curiosity; it is crucial for accurate diagnosis and treatment for more favourable long-term outcomes. Exploring their differences, starting from their basic makeup and symptoms, can guide prognosis and treatment strategies, to provide essential insight into why early detection is so important.⁵ 

Cellular differences

The two cancers come from different types of cells within the skin.⁵ SCCs originate from the squamous epithelial cells, which are flat cells that line the outermost layer of the skin in the vermillion border of the lip. This usually helps protect the body against environmental damage.⁶  

When these cells are impaired by too much sun exposure or smoking, they can become cancerous.⁶ When observed under a microscope, SCCs will demonstrate signs of structural changes with layers of hard, keratin-like material (keratin pearls) that clump together.⁷ 

On the other hand, BCCs originate from the basal cells that are located deeper down in the outer layer of the skin. This type of cancer appears on the upper lip and the skin above the vermillion border exposed to UV rays.⁸ 

When looked under a microscope, BCCs form small and dark outer edge clusters with a key feature of a ‘palisading nuclei’ - this is where the cells at the edge of these nests line up to form an abnormal fence-like pattern.⁷ There is also a small gap between the tumour cells and the surrounding tissue. 

BCCs are slow-growing and rarely spread to infect other parts of the body, unlike SCCs.⁸ These unique differences in cell type and appearance help doctors identify the exact type of lip cancer, so they can choose the most effective form of treatment for each patient. 

Clinical presentation and symptoms

SCCs and BCCs both appear on the lips, but they have isolated symptoms that show up differently. As the more aggressive and fast-growing type, up to 95% of lip cancers are SCCs, which begin as a thick and crusty area that does not heal on the lower lip, and can sometimes be mistaken for cold sores.³ It starts to bleed and becomes painful to the touch and develops a noticeable non-healing ulcer.⁵ If SCCs are not treated early, they can grow quickly in a matter of weeks, which enables the cancer to spread to nearby tissues or lymph nodes.⁶ 

In contrast, the less common BCCs more typically affect the upper lip and the skin nearby (7%).⁵ Although BCCs rarely spread to other parts of the body and tend to grow slowly over months and even years before being noticed, they can still cause local damage if symptoms are ignored. It usually presents itself as a small and shiny bump, or a smooth pearly nodule or papule, sometimes even with visible tiny blood vessels on the surface. They can be confused with a pimple that does not go away.⁸ 

Patients will experience crusting and recurrent bleeding which is often the reason they seek medical advice.⁸ Therefore, spotting these changes on the lips early and knowing what to look out for can make a real difference in catching lip cancer, so treatment can be less invasive and more successful.¹ 

Diagnosis and staging 

Diagnosing lip cancer starts with physical exams, where doctors will closely inspect any abnormality on the lips.³ If something suspicious is found, tissue biopsies are the next course of action, where a small sample of tissue is taken to be examined under a microscope to confirm whether the cancer type is squamous or basal.⁴ 

For further confirmation, imaging techniques like magnetic resonance imaging (MRI) and computed tomography (CT) may be used to dictate the growth of cancer.³ The whole process is called staging, which uses the tumour-node-metastasis (TNM) system to categorise tumours and evaluate the distribution of cancer.³ 

SCCs have a higher risk of spreading compared to BCCs, so staging is especially important to check if it has reached any lymph nodes in the neck.⁴ However, BCCs tend to grow deeper into surrounding tissues.⁸ Therefore, the combination of these examinations helps clinicians determine the stage of cancer to establish the best treatment plan and predict likely outcomes.³ 

Treatment options

The most common treatment approach for both lip cancer types is surgical removal of the cancerous growth. For small or early-stage cancers, the gold standard treatment is the Mohs technique, which removes the cancer layer by layer while preserving as much healthy tissue as possible, particularly for areas of the lip that are more delicate.⁸ The advantage of this technique is that it lowers the chances of recurrence. 

In advanced SCC cases, this may be coupled with radiotherapy to target any remaining cancer cells or treat areas that cannot be operated on easily.⁴ If SCCs have already spread to the lymph nodes, chemotherapy and targeted drug therapy may be used.⁵ Additional BCC treatment may include topical therapies or cryotherapy, which is recommended for patients who have multiple superficial cancer cells and are poor surgical candidates.⁸ 

After treatment, regular check-ups and self-monitoring are important to ensure that the cancer has not come back, as they are also at higher risk of getting lip cancer again.¹

Prognosis and outcomes

On the bright side, changes in the lips are easily noticeable, so most cases of lip cancer are caught early when the cancer is still at its initial stages (T1/ T2), making the outcomes rarely fatal. For the more aggressive cancer type, the 5-year survival rate for lip SCCs is 82.1% with a higher risk metastasis rate of 2-10%, for how quickly cancer cells spread from the primary tumour to other regions of the body. Conversely, the survival rate for BCCs exceeds 90% due to the unlikely spread of cancer cells (0.1%).⁵ The chances of recurrence for SCCs and BCCs are 12.4% and 9.6% respectively.⁵ 

Most people make full recoveries, but factors that affect these statistics include the size of the tumour, how deeply it has grown, and whether it has spread.⁴ Even though the prognosis for both types of cancer cells is generally positive when the cancer is entirely removed, there could be some long-term consequences from treatments that can compromise the patient’s quality of life, aesthetic outlook, and basic oral functions.⁵ Overall, both types have excellent prognosis with high survival rates and outcomes. Most cases can be cured with early detection and proper treatment.³ 

Summary

It is imperative to understand that even though squamous cell carcinomas and basal cell carcinomas both affect the lips, they differ in important ways from the types of cells they derive from, to how they look, behave, and their response to treatment. The importance lies in the clinicians’ ability to be able to tell the differences in diagnosis and to choose the right direction for treatment. 

SCCs are more likely to appear on the lower lip, grow quickly and spread to adjacent tissues, while BCCs usually affect the upper lip or nearby facial skin and grow slowly with little risk of spreading. With prompt care, the chances of making a full recovery are possible, and regular follow-ups can help prevent recurrence. Being aware of the signs of lip cancer and protecting your lips against carcinogenic risks such as sun damage and tobacco use can go a long way in reducing your risks of developing lip cancer.