Therapeutics in Dermatology
A reference textbook in dermatology

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Basal cell carcinoma


Basal cell carcinoma (BCC) is the most common type of skin cancer. It arises most frequently in patients aged over 50. The incidence in France is 70 cases per 100 000 inhabitants. This incidence varies depending on phototype and latitude. Thus, in countries with high levels of insolation and a generally fair-skinned population such as Australia, the incidence is high, with about 400 cases per 100 000. BCC is usually develops de novo but, in very rare cases, it can be a complication of a nevus sebaceous (of Jadasshon). The main cause is solar irradiation which explains why 80 percent of these cancers are found on exposed parts of the body, mainly the head and neck. Sporadic exposure to the sun is considered to be a more common cause than chronic exposure [1]. Some genetic conditions predispose to BCC, for example : xeroderma pigmentosum, a disorder linked to an autosomal recessive DNA repair deficiency, and nevoid basal cell carcinoma syndrome or GORLIN’S syndrome, which is caused by mutations in the Sonic Hedgehog signalling pathway. These two genodermatoses are described in separate chapters. BCC also tend to develop on radiodermatitis lesions.

There are many different forms of BCC. Several clinicopathological classifications are possible, depending on how invasive/aggressive the tumour is considered to be. The purpose of these classification systems is to standardise the management of BCCs. The French guidelines on management of adult BCC in June 2004 [2] proposes 3 clinical sub-types (nodular BCC, superficial BCC and sclerodermiform BCC, all three possibly becoming pigmented and/or ulcerated) and 4 histological sub-types (nodular BCC, superficial BCC, infiltrative BCC, which encompasses micronodular BCC and sclerodermiform BCC ; combinations of these subtypes are possible). Other classifications [3, 4] include micronodular BCCs in the nodular BCC category and sclerodermiform BCC with the infiltrative form, underlining the aggressive nature of the two types. Treatment for BCC should therefore always be guided by the results of a biopsy. The severity of BCC gradually increases from the superficial, nodular type to the sclerodermiform, ulcerating type. In patients with the mixed histological forms, the sub-type with the poorest prognosis predominates. Treatment for these tumours must also take into account other prognostic factors such as location, size and recurrent nature. These locations can be divided into low risk (body and limbs), intermediate risk (forehead, cheek, chin, scalp and neck) and high risk zones (nose and peri-orificial locations on the head). The size-linked risk of recurrence is also influenced by the location of the tumour ; the risk increases in the high-risk zones for tumours measuring more than 1 cm in diameter, and in the low or intermediate-risk zones, with tumours measuring more than 2 cm in diameter.

The French guidelines [2] proposes 3 prognostic groups :

— The poor prognosis group : this includes the clinical sclerodermiform or poorly-circumscribed forms and histologically aggressive forms (metatypical, infiltrative and sclerodermiform BCCs) ; the recurrent forms (with the exception of superficial BCCs) ; the nodular forms in high risk zones exceeding 1 cm in size.

— The good prognosis group : all primary, superficial BCCs and premalignant fibroepithelial (Pinkus) tumours ; well-defined, primary, nodular BCCs measuring less than 1 cm located in an intermediate risk zone or less than 2 cm in a low risk zone.

— The intermediate prognosis group : recurrent superficial BCCs ; nodular BCCs < 1 cm on the high risk zones, > 1 cm on the intermediate risk zones and > 2 cm on the low risk zones.

However, despite the differences in the local invasiveness of these histological forms, BCCs rarely metastasize. While the main aim of treatment is to control the cancer, these tumours tend to be located on exposed areas thus the impact they have on appearance and the patient’s comfort must also be taken into consideration. The data in the literature have shown that it is difficult to compare the various techniques without standardising follow-up methods [5, 6].

A meta-analysis reported that, irrespective of the treatment method, BCC recurrences (affecting approximately 10 percent of cases) were observed after 3 years for two thirds of the patients and after 5 years for 18 percent of them. Prolonged follow-up is therefore required to assess and compare the efficacy of the treatment methods used [7].

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