Diagnosis: Basal cell carcinoma, pigmented subtype
Basal cell carcinoma (BCC) is the most common cancer among Caucasians1 and accounts for approximately 75% of all skin cancers. Resultant mortality is very low, but it may cause destruction to local and surrounding structures. Metastasis to lymph nodes and other organs and subsequent death have been reported with BCC.2,3 Other names for BCC are basalioma, basal cell epithelioma, rodent ulcer, and Jacobs’ ulcer.
Clinical presentations: Location, subtypes, risk of recurrence
The face (particularly the nose) is the most common site for BCC. A small percentage of BCCs occur on the trunk; it is rare on areas not exposed to the sun, such as the penis, vulva, perianal areas and axilla. Many subtypes of BCCs exist, including nodular, superficial, cystic, micronodular, morpheaform, and pigmented. In addition to features seen in lesions of nodular BCC, the pigmented subtype contains increased brown or black pigment, and it is seen more commonly in persons with dark skin.
Histology and new investigations
BCC arises from the basal layer of the epidermis. There are many histologic subtypes. The basaloid cells form tumor aggregates or nests of varying sizes. Cells tend to align more densely in a palisade pattern at the periphery of these nests. In the morpheaform subtype, the cells are embedded in fibrous stroma.
In a recent article, Goldberg et al4 used histopathology and special staining to show that BCC lesions had melanin pigment (positive for Fontana-Masson stain and negative for Perl’s stain) within nests of tumor cells. The authors concluded that speckled pigmentation of a basal cell carcinoma is a distinguishing feature, which may be useful in differentiating this tumor from other discrete skin tumors.
More recently, endothelins (ETs) have been implicated as participating in the pigmentation process of BCC. Enhanced ET-1 expression in pigmented BCC plays an important role in the hyperpigmentation of this tumor.5
Risk factors for BCC: Environment, genetics
Solar radiation is the chief environmental cause of BCC. Therapeutic radiation, such as PUVA for psoriasis or radiation for the treatment of acne or tinea capitis may result in BCC many years after exposure. Genetic characteristics such as fair skin, light-colored eyes, and red hair are also important risk factors. Another reported risk factor is chronic arsenic exposure, which may result from ingestion of contaminated water or seafood.
Basal cell nevus syndrome is an autosomal dominant genetic disorder with multiple characteristic clinical features. These features include the development of multiple BCCs at a relatively young age, macrocephaly, frontal bossing, hypertelorism, bifid ribs, palmar and plantar pitting, and bone cysts in the mandible. These patients have a mutation in the tumor suppressor gene patched (PTCH) on chromosome 9.6 Xeroderma pigmentosum and other rare genetic diseases also increase the likelihood of BCC tumors. Risk of BCC recurrence is related to tumor location and size, histologic type, and treatment modality and history of UV exposure.