In a small proportion of cases, basal-cell carcinoma also develops as a result of basal-cell nevus syndrome, or Gorlin Syndrome, which is also characterized by keratocystic odontogenic tumors of the jaw, palmar or plantar (sole of the foot) pits, calcification of the falx cerebri (in the center line of the brain) and rib abnormalities. The cause of this syndrome is a mutation in the PTCH1 tumor suppressor gene located in chromosome 9q22.3, which inhibits the hedgehog signaling pathway. A mutation in the SMO gene, which is also on the hedgehog pathway, also causes basal-cell carcinoma. Diagnosis
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. Exfoliative cytology methods have high sensitivity and specificity for confirming the diagnosis of basal cell carcinoma when clinical suspicion is high but unclear usefulness otherwise. Characteristics
Basal-cell carcinoma cells appear similar to epidermal basal cells, and are usually well differentiated.In uncertain cases, immunohistochemistry using BerEP4 can be used, having a high sensitivity and specificity in detecting only BCC cells. Main classes
Basal-cell carcinoma can broadly be divided into three groups, based on the growth patterns. Superficial basal-cell carcinoma, formerly referred to in-situ basal-cell carcinoma, is characterized by a superficial proliferation of neoplastic basal-cells.
Other subtypes
Other more specific subtypes of basal-cell carcinoma include:: 646–50

Aggressiveness patterns
There are mainly three patterns of aggressiveness, based mainly the cohesion of cancer cells:

Differential diagnoses
Radicality
In suspected but uncertain BCC cells close to the resection margins, immunohistochemistry with BerEp4 can highlight the BCC cells. Prevention
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. The review did ultimately state that the certainty of these results was 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.The use of a chemotherapeutic agent such as 5-Fluorouracil or imiquimod can prevent the development of skin cancer. It is usually recommended to individuals with extensive sun damage, history of multiple skin cancers, or rudimentary forms of cancer (i.e., solar keratosis). It is often repeated every 2 to 3 years to further decrease the risk of skin cancer. Treatment
The following methods are employed in the treatment of basal-cell carcinoma (BCC):

Standard surgical excision
Surgery to remove the basal-cell carcinoma affected area and the surrounding skin is thought to be the most effective treatment.