Squamous cell carcinoma

A large head and neck squamous cell carcinoma of the tongue as seen on CT imaging

nder a microscope. Squamous cell carcinomas (SCCs), also known colloquially as epidermoid carcinomas, represent a diverse array of cancers that originate from squamous cells. These cells primarily constitute the outer layer of the skin and line the internal and hollow structures of the body, including the respiratory and digestive tracts.

Classification of Squamous Cell Carcinomas

A variety of SCCs have been identified, each associated with distinct areas of the body. However, despite sharing the name "squamous cell carcinoma", these different types can exhibit variations in symptoms, natural progression, prognosis, and response to treatments.

The common types of SCCs include:

Squamous cell skin cancer: A subtype of skin cancer Squamous-cell carcinoma of the lung: A form of lung cancer Squamous cell thyroid carcinoma: A classification of thyroid cancer Esophageal squamous cell carcinoma: A form of esophageal cancer Squamous-cell carcinoma of the vagina: A category of vaginal cancer

Causal Factors and Locations

The presence of Human papillomavirus infection has been strongly associated with the development of SCCs in various areas of the body, such as the oropharynx, lung, fingers, and anogenital region.

Head and Neck SCCs

A large head and neck squamous cell carcinoma of the tongue as seen on CT imaging

Main article: Head and neck cancer

Head and neck cancer refers to malignancies affecting the mouth, nasal cavity, nasopharynx, throat, and related structures. Around 90% of these cases are attributed to SCC.

Thyroid SCCs

Main article: Squamous cell thyroid carcinoma

Primary squamous cell thyroid carcinoma is notable for its aggressive behavior, leading to a poor prognosis.

Risk Factors and Causes

Various factors contribute to the development of squamous cell carcinomas (SCCs), including exposure to carcinogenic agents, immune suppression, and certain viral infections. Human papillomavirus infection, in particular, has been linked with SCCs in various body locations such as the oropharynx, lungs, fingers, and anogenital region. It is worth noting that HPV-16 and HPV-18 are especially implicated in the development of SCCs in the penis.

The risk of SCC development also increases with chronic inflammation and scar tissues. For instance, Marjolin's ulcer, a type of SCC, arises from nonhealing ulcers or burn wounds. Chronic conditions, such as the parasitic infection schistosomiasis, are also associated with SCC, particularly in the bladder.

Treatment and Prognosis

The treatment for SCCs can vary significantly depending on the location and stage of the disease. Despite all being classified under the umbrella of "squamous cell carcinoma", SCCs that develop in different body sites can display variations in their symptoms, natural history, prognosis, and response to treatment.

Surgery is often a primary mode of treatment for localized disease, such as esophageal squamous cell carcinoma. If the disease has spread, however, chemotherapy and radiotherapy are commonly used. For some specific types of SCCs like squamous cell carcinoma of the prostate, early detection is particularly challenging, which often leads to diagnosis at an advanced stage. The prognosis for such cancers is generally poor.

Diagnosis

A diagnosis of SCC typically involves medical history evaluation, a physical examination, and medical imaging. The confirmation of the diagnosis is generally established through a biopsy, followed by histopathology. TP63 staining is the primary histological marker for SCC, and TP63 is an essential transcription factor to establish squamous cell identity.

SCCs can be further classified into different histopathological subtypes, such as adenoid squamous cell carcinoma, basaloid squamous cell carcinoma, clear-cell squamous cell carcinoma, and signet ring-cell squamous cell carcinoma. Each subtype is characterized by unique microscopic features and clinical behaviors.

Prevention

Modifiable lifestyle factors, particularly dietary habits, have been found to influence the risk of SCC development. High-fat dairy food consumption, for instance, has been linked to increased SCC tumor risk in individuals with previous skin cancer. On the other hand, consuming green leafy vegetables may help prevent the development of subsequent SCC. Other protective food groups against SCC risk include raw vegetables and fruits, both citrus and non-citrus.

Despite the variations in SCC's characteristics and behaviors depending on the location, understanding the shared risk factors, diagnosis techniques, and preventive measures can facilitate the management and treatment of this group of cancers.

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  Adenoid squamous cell carcinoma

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  Basaloid squamous cell carcinoma

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  Clear-cell squamous cell carcinoma

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  Spindle-cell squamous cell carcinoma

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