3.3.5 Basal Cell Carcinoma

The incidence in Europe is 450 to 500/100,000/year. Incidence in US is 1,019/100,000/y in women and 1,488/100,000/year in men. It is the most common skin malignancy.

Predisposing factors are skin types I and II, UV exposure, immunosuppression, radiation, arsenic exposure/ingestion, and genetic. Naevoid basal cell carcinoma syndrome (Gorlin-Goltz syndrome) is a genetic predisposition for multiple basal cell carcinomas. Most, if not all, cases of BCC demonstrate overactive Hedgehog signalling.

Lesions are usually located on the face (85%), less often on trunk or extremities. In contrast to squamous cell carcinoma, they are not restricted to sun-exposed areas.

There are no precursor lesions. Classification is done due to clinical (C) or histological (H) features.

• Superficial BCC (C)

• Nodular (solid) BCC (C)

• Sclerodermiform (Morphaeic infiltrating) BCC (C and H)

• Adenocystic BCC (H)

• Pigmented BCC (C)

• Baso-squamous BCC (H)

• Dedifferentiated BCC (H)

• Ulcus rodens (C)

• Ulcus terebrans (C)

• Genetically based BCC such as Gorlin-Goltz syndrome (basal cell nevus syndrome) (C)

Histology shows proliferation of basaloid cells streaming downwards from the basal cell layer of the epidermis or from follicular epithelium in upper dermis, peripheral palisading cell layer (darker row of cells at periphery), mitoses, and single cell necrosis (apoptosis).

There are subtypes which mimic abnexal structures of the skin. In the infiltrating type may show dedifferentiation and carcinoma-like pattern.

Lesions run a slow progressive course of peripheral or vertical extension. They may become ulcerated and locally extensive. Metastases in BCC are extremely rare.

Basal cell carcinoma must be differentiated from dermal naevi, sebaceous gland hyperplasia, fibroma, pseudolymphoma, melanoma, carcinoma in situ (Bowen disease or Paget disease), actinic keratosis and tumors of skin adnexal tumors.

Prevention

UV-light protection is essential.

Treatment depends on the type, size and location. Surgical excision with appropriate margins is the main treatment but recurrences may occur. For the sclerosing tumour type, micrographic control of margins is mandatory. Curettage, radiation therapy and cryosurgery can also be used in the small superficial types. Superficial variants can also be treated with photodynamic therapy, topical 5-fluorouracil, immunotherapy (imiquimod) or ablative laser with monitoring follow up.

New targeted therapies with inhibition of hedgehog pathway may be indicated in advanced cases (Vismodegib, Sonidegib).