Ans. is 'd' i.e., All the above Squamous Cell Carcinoma:* Squamous cell carcinoma is the second most common tumor arising on sunexposed sites in older people, exceeded only by basal cell carcinoma.* Except for lesions on the lower legs, these tumors have a higher incidence in men than in women.* Invasive squamous cell carcinomas are usually discovered while they are small and resectable.* Less than 5% of these tumors metastasize to regional nodes; these lesions are generally deeply invasive and involve the subcutis.* The most important cause of cutaneous squamous cell carcinoma is DNA damage induced by exposure to UV light.* Tumor incidence is proportional to the degree of lifetime sun exposure.* A second common association is with immunosuppression, most notably chronic immunosuppression as a result of chemotherapy or organ transplantation.* Immunosuppression may contribute to carcinogenesis by reducing host surveillance and increasing the susceptibility of keratinocytes to infection and transformation by oncogenic viruses, particularly human papilloma virus (HPV) subtypes 5 and 8. These same HP Vs have been implicated in tumors arising in patients with a rare autosomal recessive condition, epidermodysplasia verruciformis, which is marked by a high susceptibility to cutaneous squamous cell carcinomas.* In addition to its damaging effect on DNA, sunlight, through uncertain mechanisms, seems to cause a transient defect in cutaneous innate immunity that may diminish immunemediated elimination of sun-damaged cells.* Other risk factors for squamous cell carcinoma include industrial carcinogens (tars and oils), chronic ulcers and draining osteomyelitis, old burn scars, ingestion of arsenicals, ionizing radiation, and (in the oral cavity) tobacco and betel nut chewing.* Most studies on the genetics of squamous cell carcinoma have focused on acquired defects in sporadic tumors and their precursors (actinic keratoses), and the relationships between these defects and sun-exposure.* The patients patients with xeroderma pigmentosum show remarkable susceptibility to squamous cell carcinoma.* As with all other forms of cancer, cutaneous squamous cell carcinoma stems from multiple driver mutations.* In addition to defects in p53, mutations that increase RAS signaling and decrease Notch signaling are common and are also likely to contribute to the transformation process.