What is squamous carcinoma
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Understanding Squamous Cell Carcinoma (SCC)
Definition and General Characteristics of Squamous Cell Carcinoma
Squamous Cell Carcinoma (SCC) is a type of cancer that originates from squamous cells, which are flat cells found in the outer layer of the skin and in the lining of various organs. SCC is characterized by the malignant transformation of these epithelial cells, leading to invasive growth and potential metastasis .
Epidemiology and Risk Factors
Skin and Eyelid SCC
SCC is the second most common type of non-melanoma skin cancer, often arising from epidermal keratinocytes. Chronic sun exposure is a significant risk factor, particularly for cutaneous SCC, which frequently develops on sun-damaged skin . It is also the second most common eyelid malignancy among Caucasians, where it can be misdiagnosed due to its clinical similarity to basal cell carcinoma (BCC).
Head and Neck SCC
Head and neck squamous cell carcinoma (HNSCC) is the most common non-cutaneous malignancy in this region. Risk factors include tobacco use, alcohol consumption, and infection with oncogenic viruses such as human papillomavirus (HPV) . The incidence of HPV-associated oropharyngeal cancer is notably increasing in developed countries.
Lung SCC
Squamous-cell carcinomas of the lung (SQCLCs) were historically the most common subtype of non-small-cell lung cancers. These tumors are now surpassed by adenocarcinomas but remain significant due to their unique molecular characteristics and high complexity.
Molecular and Genetic Insights
SCCs exhibit a range of genetic alterations that contribute to their development and progression. Common genetic changes include mutations in tumor suppressor genes and activation of proto-oncogenes such as p16ink4A, p53, cyclin D1, and EGFR. In lung SCC, specific mutations like SOX2 amplification, NFE2L2 and KEAP1 mutations, and changes in the PI3K pathway have been identified, leading to new targeted therapies.
Clinical Presentation and Diagnosis
SCC can present with various clinical features depending on its location. For instance, cutaneous SCC often appears as a persistent, scaly, and sometimes ulcerated lesion on sun-exposed areas. In the head and neck region, SCC may manifest as a non-healing ulcer or mass, often requiring biopsy for definitive diagnosis . Histopathological examination is crucial, as nearly all cutaneous SCCs show evidence of in situ changes, indicating their progression from actinic keratosis.
Treatment and Management
Skin SCC
Treatment options for cutaneous SCC include surgical excision, Mohs micrographic surgery, electrodessication and curettage, cryosurgery, radiotherapy, and topical medications. The choice of treatment depends on the lesion's risk stratification.
Head and Neck SCC
Early-stage HNSCC is typically treated with single-modality therapy, either surgery or radiotherapy. Locally advanced cases require multimodal treatment, including surgery followed by adjuvant radiation or chemoradiation. For recurrent or metastatic disease, chemotherapy with or without biological agents is indicated.
Lung SCC
The treatment of lung SCC has evolved with the discovery of specific genetic mutations, leading to the development of targeted therapies. These include agents targeting the PI3K pathway, FGFR1, and DDR2 mutations, among others.
Conclusion
Squamous cell carcinoma is a diverse and complex group of cancers arising from squamous cells in various body sites. Understanding its epidemiology, molecular biology, and clinical presentation is crucial for effective diagnosis and treatment. Advances in genetic research and targeted therapies offer promising avenues for improving patient outcomes across different types of SCC.
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