It is very appropriate this summer to talk about the Sun and skin cancer. We also know that a little exposure to the Sun helps activate the famous Vitamin D at the skin level. In fact, exposing the forearm to the Sun for twenty minutes three times a week is enough to activate Vitamin D and is healthy.
Exposing oneself to solar rays excessively is known to be a risk for various types of skin cancer. Not to mention wrinkles and having skin that is shriveled and aged due to the damage that UV (ultraviolet) rays cause to the skin.
The types of skin cancer vary from bad to very bad, from invasive and destructive to progressively destructive. Many types of skin cancer are curable, especially if diagnosed in time.
UV rays do not only come from the Sun. Tanning beds or “tanning salons” emit these dreaded UV rays and are not recommended.
Countries where the Sun shines all day, like some states in Brazil, Australia, and other countries, are especially hit by very high numbers of skin cancer. It is so common that statistics get lost. Doctors cure this type of cancer but do not notify health authorities, and statistics are not rigorously calculated.
Basal cell carcinoma is a very common type of skin cancer, appearing in the basal layer of the epidermis. Although these tumors have a low potential for metastasis (spreading), they can be locally invasive and destructive to the skin and neighboring structures.
Basal cell cancer is the most common among white people and its incidence is rising worldwide. Basal cell cancer is associated with exposure to UV rays, especially during childhood. The 
majority of other risk factors act through an interaction with UV exposure. About 70% of cases of this type of cancer affect the face and head. The most common presentation of this basal cancer is nodular and superficial, representing 90% of cases.
Biopsies are important to determine the cellular subtype of the cancer. Especially when there is doubt in the diagnosis, such as when there is no family history of skin cancer, the lesion exhibits a typical aspect of recurrence, or when the tumor is atypical.
Once the diagnosis is established, appropriate treatment offers a high probability of cure, despite the patient being at greater risk of developing other skin malignancies.
Another type of skin cancer is squamous cell cancer. Also linked to UV exposure, this type of skin cancer can develop on any skin surface, including the head and neck (55%), torso, extremities, oral mucosa, skin between the nails, and anogenital areas. In light-skinned individuals, this cancer appears in areas more exposed to the Sun. Involvement of cancer in parts of the skin less exposed to the Sun is more common in dark-skinned individuals.
Typically, squamous cell skin cancer manifests with erythematous papules (reddish skin elevations), plaques, or nodules. Ulceration or hyperpigmentation is also common. Squamous cancer can appear in chronic wounds, chronic inflammation, or areas of scarring. Non-healing ulcers or nodules in these areas may be signs of squamous cancer.
Biopsy is always necessary to confirm the diagnosis.
Actinic keratosis or sun-induced spots can resemble squamous cancer. Painful lesions or those containing a substance should also be investigated with biopsy.
Another type of skin cancer is the dreaded melanoma. There are four different types of melanoma: superficial invasive melanoma, malignant lentigo melanoma, acral lentiginous melanoma, and nodular melanoma. Other less common variants exist, such as amelanotic melanoma, spitzoid melanoma, and desmoplastic melanoma. The thickness of the tumor is key to prognosis (success or failure in treatment) for patients with melanoma. Patients with tumors less than 1 mm thick have a 10-year survival rate of 92%, while patients with tumors thicker than 4 mm have a 10-year survival rate reduced to 50%.
Family or personal history of melanoma, habits of sun exposure, and history of sunburns, presence of fair skin, and skin lesions (nevi) are important aspects in the diagnosis and evaluation of melanoma. Early signs of melanoma include asymmetry of the lesion, irregular borders, varied colors, a diameter of more than 6 mm, and a recent change in size or the appearance of a new skin spot, particularly in adults. A skin lesion that looks different from others you have, that appears to be the ugliest of all your spots, may be a melanoma and deserves to be seen by your doctor.
New imaging technologies, including dermatoscopy, confocal microscopy, and multispectral imaging, are recent developments for early recognition of melanoma. Not all dermatologists have these technical modalities, but most doctors know how to differentiate a melanoma from another 
skin lesion. A wide biopsy, including the full thickness of the lesion with margins of 1 to 3 mm of normal skin around the lesion, is important, along with some subcutaneous fat if possible. The definitive diagnosis of melanoma is histopathological (microscopic), including immunohistochemical stains in doubtful cases.
The general practitioner who identifies a lesion suspected of being a melanoma should refer the patient to a dermatologist who has other diagnostic modalities, including a dermatoscope, and assess whether a biopsy is necessary.
A change in an old skin lesion or a new and persistent skin lesion, especially if pigmented and growing in size or ulcerated (bleeding), are the main indications for referral to a specialist. Other indications include when the lesion has three different colors, is asymmetrical, itches or bleeds, a pigmented lesion on the nail, particularly if associated with damage to the nail growth plate, and any lesion that arises under the nail should raise suspicion of malignancy.