Instruct: Given a question, retrieve documents that answer the question.
Query: How common are basal cancerous cells?
Basal-cell cancer is a very common skin cancer. It is much more common in fair-skinned individuals with a family history of basal-cell cancer and increases in incidence closer to the equator or at higher altitude. There are approximately 800,000[55] new cases yearly in the United States alone. Up to 30% of Caucasians develop basal-cell carcinomas in their lifetime.[56] In Canada, the most common skin cancer is basal-cell carcinoma (as much as one third of all cancer diagnoses), affecting 1 in 7 individuals over a lifetime.[57]
More than 3.5 million cases of skin cancer are diagnosed annually in the United States, which makes it the most common form of cancer in that country. One in five Americans will develop skin cancer at some point of their lives. The most common form of skin cancer is basal-cell carcinoma, followed by squamous cell carcinoma. Unlike for other cancers, there exists no basal and squamous cell skin cancers registry in the United States.
Nevoid basal-cell carcinoma syndrome (NBCCS), also known as basal-cell nevus syndrome, multiple basal-cell carcinoma syndrome, Gorlin syndrome, and Gorlin–Goltz syndrome, is an inherited medical condition involving defects within multiple body systems such as the skin, nervous system, eyes, endocrine system, and bones. People with this syndrome are particularly prone to developing a common and usually non-life-threatening form of non-melanoma skin cancer. About 10% of people with the condition do not develop basal-cell carcinomas (BCCs). 
Basal cell carcinoma makes up about 1–2% of vulvar cancer. These tend to be slow-growing lesions on the labia majora but can occur anywhere on the vulva. Their behavior is similar to basal cell cancers in other locations. They often grow locally and have low risk for deep invasion or metastasis.
Basal-cell carcinomas are present on sun-exposed areas of the skin, especially the face. They rarely metastasize and rarely cause death. They are easily treated with surgery or radiation. Squamous-cell skin cancer are common, but much less common than basal-cell cancers. They metastasize more frequently than BCCs. Even then, the metastasis rate is quite low, with the exception of SCC of the lip, ear, and in people who are immunosuppressed. Melanoma are the least frequent of the 3 common skin cancers. They frequently metastasize, and could potentially cause death once they spread.
The cure rate with Mohs surgery cited by most studies is between 97% and 99.8% for primary basal-cell carcinoma, the most common type of skin cancer. Mohs procedure is also used for squamous cell carcinoma, but with a lower cure rate. Recurrent basal-cell cancer has a lower cure rate with Mohs surgery, more in the range of 94%. It has been used in the removal of melanoma-in-situ (cure rate 77% to 98% depending on surgeon), and certain types of melanoma (cure rate 52%). 
Patients with ocular sebaceous carcinomas present with nonhealing eyelid tumors that are often misdiagnosed for more common benign conditions such as chalazion or bleproconjunctivitis. Extraocular SGc appears similarly to skin cancers such as basal cell carcinoma, squamous cell carcinoma and benign lesions such a molluscum contagiosum and pyogenic granuloma. Many tumors also share a histological presentation similar to SGC, such as sebaceous adenomas, basal cell carcinomas (BCC), squamous cell carcinomas (SCC) and clear cell tumors. A high level of suspicion is extremely important to prevent treatment delay and increased mortality.
A weakness with standard surgical excision is the high recurrence rate of basal-cell cancers of the face, especially around the eyelids,[33] nose, and facial structures.[35] There is no clear approach for treating basal-cell carcinoma around the eye.[36] A diagram on page 38 of the National Comprehensive Cancer Network publication demonstrate the area of high risk of recurrence as being most of the face with the exception of the central cheek and upper forehead.[26] On the face, or on recurrent basal-cell cancer after previous surgery, special surgical margin controlled processing (CCPDMA—complete circumferential peripheral and deep margin assessment[26])[37] using frozen section histology (Mohs surgery is one of the methods) is required.[38][39]
Nasopharynx cancer or nasopharyngeal carcinoma (NPC) is the most common cancer originating in the nasopharynx, most commonly in the postero-lateral nasopharynx or pharyngeal recess or 'Fossa of Rosenmüller' accounting for 50% cases. NPC occurs in children and adults. NPC differs significantly from other cancers of the head and neck in its occurrence, causes, clinical behavior, and treatment. It is vastly more common in certain regions of East Asia and Africa than elsewhere, with viral, dietary and genetic factors implicated in its causation. It is most common in males. It is a squamous cell carcinoma or an undifferentiated type. Squamous epithelial cells are a flat type of cell found in the skin and the membranes that line some body cavities. Differentiation means how different the cancer cells are from normal cells. "Undifferentiated cells" are cells that do not have their mature features or functions.
SCC of the skin begins as a small nodule and as it enlarges the center becomes necrotic and sloughs and the nodule turns into an ulcer.Squamous cell carcinoma is the second-most common cancer of the skin (after basal-cell carcinoma but more common than melanoma). It usually occurs in areas exposed to the sun. Sunlight exposure and immunosuppression are risk factors for SCC of the skin, with chronic sun exposure being the strongest environmental risk factor. There is a risk of metastasis starting more than 10 years after diagnosable appearance of squamous cell carcinoma, but the risk is low, though much higher than with basal-cell carcinoma. Squamous cell cancers of the lip and ears have high rates of local recurrence and distant metastasis. In a recent study, it has also been shown that the deletion or severe down-regulation of a gene titled Tpl2 (tumor progression locus 2) may be involved in the progression of normal keratinocytes into becoming squamous cell carcinoma.
To diagnose basal-cell carcinomas, a skin biopsy is performed for histopathologic analyses. The most common method is a shave biopsy under local anesthesia. Most nodular basal-cell cancers can be diagnosed clinically; however, other variants can be very difficult to distinguish from benign lesions such as intradermal naevus, sebaceomas, fibrous papules, early acne scars, and hypertrophic scarring.[16]
About two thirds of basal-cell carcinomas occur on sun-exposed areas of the body. One-third occur on areas of the body that are not exposed to sunlight, emphasizing the genetic susceptibility of basal-cell cancer.
Individuals with a basal-cell carcinoma typically present with a shiny, pearly skin nodule. However, superficial basal-cell cancer can present as a red patch similar to eczema. Infiltrative or morpheaform basal-cell cancers can present as a skin thickening or scar tissue – making diagnosis difficult without using tactile sensation and a skin biopsy. It is often difficult to visually distinguish basal-cell cancer from acne scar, actinic elastosis, and recent cryodestruction inflammation.
Treatment is dependent on the specific type of cancer, location of the cancer, age of the person, and whether the cancer is primary or a recurrence. For a small basal-cell cancer in a young person, the treatment with the best cure rate (Mohs surgery or CCPDMA) might be indicated. In the case of an elderly frail man with multiple complicating medical problems, a difficult to excise basal-cell cancer of the nose might warrant radiation therapy (slightly lower cure rate) or no treatment at all. Topical chemotherapy might be indicated for large superficial basal-cell carcinoma for good cosmetic outcome, whereas it might be inadequate for invasive nodular basal-cell carcinoma or invasive squamous-cell carcinoma. In general, melanoma is poorly responsive to radiation or chemotherapy.
Hydrogenosomes are considered to be of scientific interest because comparing them with mitochondria may cast light on how all eukaryotic cells evolved. Hosting mitochondria appears to be a basal or near-basal trait among eukaryotes, the study of hydrogenosomes may shed light on how all multi-celled life developed. For example: Which came first: mitochondria, or hydrogenosomes, or some common ancestor?
There are three main types of skin cancer: basal-cell skin cancer (basal-cell carcinoma) (BCC), squamous-cell skin cancer (squamous-cell carcinoma) (SCC) and malignant melanoma.
Superficial basal-cell carcinoma, formerly referred to in-situ basal-cell carcinoma, is characterized by a superficial proliferation of neoplastic basal-cells. This tumor is generally responsive to topic chemotherapy, such as imiquimod, or fluorouracil. Infiltrative basal-cell carcinoma, which also encompasses morpheaform and micronodular basal-cell cancer, is more difficult to treat with conservative methods, given its tendency to penetrate into deeper layers of the skin. Nodular basal-cell carcinoma includes most of the remaining categories of basal-cell cancer. It is not unusual to encounter heterogeneous morphologic features within the same tumor.
Basal-cell cancer accounts for at least 32% of all cancers globally.[7][11] Of skin cancers other than melanoma, about 80% are basal-cell cancers.[2] In the United States, about 35% of white males and 25% of white females are affected by BCC at some point in their lives.[2]
Lung cancer is responsible for 1.3 million deaths worldwide annually, and is the most common cause of cancer-related death in men and the second most common in women. The most common cause of lung cancer is long-term exposure to tobacco smoke. Lung cancer in non-smokers, who account for approximately 15% of cases, is often attributed to a combination of genetic factors, radon gas, asbestos, and air pollution. 
The main types of lung cancer are non-small cell lung carcinoma and small cell lung carcinoma, the two being distinguished histologically as well as by how they are treated; non-small cell lung carcinoma is primarily treated with surgery if feasible, while small cell lung carcinoma is more frequently treated with chemotherapy and radiation.
The mortality rate of basal-cell and squamous-cell carcinoma is around 0.3%, causing 2000 deaths per year in the US. In comparison, the mortality rate of melanoma is 15–20% and it causes 6500 deaths per year. Even though it is much less common, malignant melanoma is responsible for 75% of all skin cancer-related deaths.
It is used to stain basal cells in prostatic glands; loss of basal cells is seen in prostate adenocarcinoma (the most common form of prostate cancer).
Basal-cell carcinoma is a common skin cancer and occurs mainly in fair-skinned patients with a family history of this cancer. Sunlight is a factor in about two-thirds of these cancers; therefore, doctors recommend sunscreens with at least SPF 30. However, a Cochrane review examining the effect of solar protection (sunscreen only) in preventing the development of basal-cell carcinoma or cutaneous squamous cell carcinoma found that there was insufficient evidence to demonstrate whether sunscreen was effective for the prevention of either of these keratinocyte-derived cancers.[19] The review did ultimately state that the certainty of these results were low, so future evidence could very well alter this conclusion. One-third occur in non-sun-exposed areas; thus, the pathogenesis is more complex than UV exposure as the cause.
Prognosis is excellent if the appropriate method of treatment is used in early primary basal-cell cancers. Recurrent cancers are much harder to cure, with a higher recurrent rate with any methods of treatment. Although basal-cell carcinoma rarely metastasizes, it grows locally with invasion and destruction of local tissues. The cancer can impinge on vital structures like nerves and result in loss of sensation or loss of function or rarely death. The vast majority of cases can be successfully treated before serious complications occur. The recurrence rate for the above treatment options ranges from 50 percent to 1 percent or less.
The most common epitheliomas are basal cell carcinoma and squamous cell carcinoma (skin cancers).
Activation of the hedgehog pathway has been implicated in the development of cancers in various organs, including brain, lung, mammary gland, prostate and skin. Basal cell carcinoma, the most common form of cancerous malignancy, has the closest association with hedgehog signaling. Loss-of-function mutations in Patched and activating mutations in Smoothened have been identified in patients with this disease. Abnormal activation of the pathway probably leads to development of disease through transformation of adult stem cells into cancer stem cells that give rise to the tumor. Cancer researchers hope that specific inhibitors of hedgehog signaling will provide an efficient therapy for a wide range of malignancies.