Basal cell versus squamous cell cancer
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Basal Cell Carcinoma vs. Squamous Cell Carcinoma: A Comparative Analysis
Introduction to Non-Melanoma Skin Cancers
Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are the most common types of non-melanoma skin cancers (NMSC) in humans, with BCC being approximately 4 to 5 times more prevalent than SCC . Both types of cancer can cause significant local destruction and disfigurement, although they rarely metastasize.
Tumor Microenvironment and Immunosuppression
The tumor microenvironment (TME) plays a crucial role in the progression of both BCC and SCC. In both cancers, the TME creates an immunosuppressed environment by downregulating effector CD4+ and CD8+ T cells and promoting the release of pro-oncogenic Th2 cytokines. This understanding has led to the development of immunotherapeutic agents such as vismodegib for BCC and cemiplimab for SCC.
Genetic and Molecular Differences
BCC and SCC exhibit distinct genetic and molecular characteristics. BCCs typically show chromosome loss confined to a single chromosome arm, particularly 9q, whereas SCCs display more widespread chromosomal losses, including 9p, 13q, 17p, 17q, and 3p. These differences suggest that the genetic pathways involved in the development of these cancers are distinct.
Epidemiology and Incidence Trends
The incidence of both BCC and SCC is rising rapidly. In the U.S., more than 1 million cases of NMSC are diagnosed annually. A study in Olmsted County, Minnesota, reported that the age-adjusted incidence rates for BCC were 360.0 per 100,000 person-years in men and 292.9 in women, while for SCC, the rates were 207.5 in men and 128.8 in women. The anatomical distribution of these cancers has also shifted over time, with BCCs moving from the head and neck to the torso and SCCs from the head and neck to the extremities.
Risk Factors and Prognosis
Several factors influence the risk of recurrence and metastasis in BCC and SCC. High-risk factors include prior tumors, ill-defined borders, aggressive histologic patterns, and perineural invasion. Patients with rheumatoid arthritis, particularly those treated with tumor necrosis factor (TNF) inhibitors, have an increased risk of developing both BCC and SCC.
Diagnosis and Treatment
BCC commonly appears as a shiny, pearly papule with a smooth surface and rolled borders, while SCC typically presents as a firm, smooth, or hyperkeratotic papule or plaque. Diagnosis often involves a shave technique for raised lesions or a punch biopsy for more abnormal-appearing areas. Treatment options vary based on the tumor's size and risk factors, ranging from surgical excision and Mohs micrographic surgery to topical treatments like imiquimod and fluorouracil.
Conclusion
While BCC and SCC share some commonalities as non-melanoma skin cancers, they differ significantly in their genetic makeup, incidence rates, and clinical presentations. Understanding these differences is crucial for developing targeted therapies and improving patient outcomes. Continued research into the tumor microenvironment and genetic factors will likely yield new insights and treatment options for these prevalent skin cancers.
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