Basal cell carcinoma (BCC) is the most common cancer in humans and the most common cancer of the skin. It is a neoplasm of basal keratinocytes that is found more frequently in men than women and is typically seen on the face. Rates of BCC have been increasing over the last several decades, particularly in young women. Nonetheless, the malignancy has greater incidence in older individuals, with a median age at diagnosis of 68 years.

There are many subtypes of BCC, including nodular, superficial, infundibulocystic, fibroepithelial, morpheaform (sclerosing, desmoplastic), infiltrative, micronodular, and basosquamous. Nodular BCC is the most common subtype overall and accounts for half of all lesions. In Black and Hispanic patients, BCCs are more often pigmented BCCs.

The most prevalent risk factor contributing to the development of BCCs is sun exposure. Other risk factors for BCCs include environmental exposure (ie, ionizing radiation, indoor tanning, chemicals such as arsenic, psoralen plus UVA, and coal tar), phenotype (freckling, red hair, light skin that always burns and never tans), immunosuppression such as organ transplantation (which results in a 5-10 times higher risk of BCCs than the general population), and various genetic syndromes including xeroderma pigmentosum, oculocutaneous albinism, Muir-Torre syndrome, basal cell nevus syndrome (Gorlin syndrome), Rombo syndrome, and Bazex-Dupré-Christol syndrome. The gene most frequently altered in BCCs is the PTCH1 gene, followed by the TP53 gene.

Although BCCs typically arise in hair-bearing areas, they can rarely be seen in hairless genital mucosa for an unknown reason. BCC of the penis and scrotum is exceedingly rare and defies conventional understanding of the disease, as these areas are unlikely to receive much sun exposure and BCCs on these areas arise even on non-hair-bearing skin. Despite the lack of sun exposure, the incidence of penile BCC is higher in male patients with light skin phototypes. BCC occurs with equal frequency on the penile shaft and the scrotum and is usually a solitary lesion. Less often, BCC will be found on the glans or the foreskin.

Although BCCs are almost never fatal, local tissue destruction and disfiguration occur. The metastasis rate of BCCs is approximately 1 in 35 000. Metastasis is rare and typically occurs through perineural spread, lymph node metastasis, and then lung / bone metastasis.