Editors

AlexanderSalava

SariKoskenmies

Basal Cell Carcinoma

Essentials

Basal cell carcinoma (BCC) is the result of uncontrolled multiplication of epidermal basal cells.
It is the most common malignant skin tumour in white people.
The malignant nature of BCC refers to the fact that it continues to grow and is able to penetrate the deeper tissues.
It does not normally metastasize.
Susceptibility to BCC depends on the amount of sun exposure over a lifetime (see also the articles on Squamous cell carcinoma Squamous Cell Carcinoma and Precancerous lesions preceding squamous cell carcinoma Precancerous Lesions Preceding Squamous Cell Carcinoma (Actinic Keratosis and Carcinoma in Situ, or Bowen's Disease)).
BCC can be prevented by avoiding UV exposure from the sun, e.g. by using sunscreens, protective clothing and a wide-brimmed hat.

Diagnosis

BCC can often be detected even clinically but the diagnosis can only be confirmed by a tumour biopsy.
Histological types
- Low-grade tumours, such as superficial, nodular, pigmented BCC
- High-grade tumours, such as infiltrating, sclerosing, micronodular BCC
- See also Table T2.
A superficial BCC is typically a clearly demarcated erythematous lesion with slight scaling (pictures 2 3).
A nodular BCC is typically a skin-coloured, clearly demarcated plaque or papule with a sunken centre and telangiectatic surface vessels. Nodular BCC most commonly occurs on the face (pictures 5 6) or the ears, whereas the superficial type is most commonly encountered on the trunk.
High-grade tumours may be indistinctly defined and with a scar-like appearance, but they are often clinically impossible to distinguish from low-grade tumours. The final diagnosis is histological.

Treatment Interventions for Basal Cell Carcinoma of the Skin

Left untreated, BCC continues to grow slowly over months and years. The speed of growth shows wide interpersonal variation. Very aggressive and fast growing types are also seen, particularly in immunosuppressed patients.
The recommended treatments are presented in Table T1.
Small basal cell carcinomas in safe skin areas can be removed in primary or outpatient health care, with follow-up at 6 to 12 months, as considered appropriate.

Surgical treatment

High-grade or nodular BCC should primarily be treated operatively (Table T1).
Surgery can also be used to treat superficial BCC, instead of using non-surgical treatment.
The lesion should be removed under local anaesthesia with a 3-5-mm margin of healthy tissue (clinical surgical margin, Table T1). After removal, the sample shrinks and hence the histological margin reported by the pathologist is always smaller than the clinical surgical margin. If a reconstruction is required, it can be achieved with a skin flap or free skin graft.
If BCC was incompletely removed, either scar excision or non-surgical treatment should be used on a case-by-case basis to prevent recurrence. Mere follow-up of the situation is in these cases not acceptable.
Nodular and histologically high-grade BCC subtypes (sclerosing, micronodular, perineural or other infiltration) in the facial area, in particular, are usually operated on in specialized care. When occurring on the trunk or limbs, these subtypes can also be operated on in primary or outpatient care by a physician with adequate expertise.

Treatment alternatives for basal cell carcinoma according to risk classification. Source: Hernberg M, Ilmonen S, Juteau S, Jääskeläinen A-S, Koljonen V, et al. Finnish guideline for the treatment of non-melanoma skin cancers. Duodecim Publishing Company 2020.

	First-line treatment	Second-line treatment	Clinical surgical margin	Histological surgical margin
Superficial BCC
Small (head, trunk, upper and lower limbs)	Freezing¹ or CO₂laser, or ED in lower limbs	PDT × 2² or surgical excision	3 mm	1 mm
Large or on a lower limb	PDT × 2 (freezing after due consideration)	Surgical excision or treatment with ointments³	3-5 mm depending on location	>1 mm
Nodular and fibroepithelioma (Pinkus tumour)	Surgical excision	Freezing after due consideration	3 mm	1 mm
High-grade BCC	Surgical excision	Postsurgical or adjuvant radiotherapy, as necessary	4-5 mm depending on location	2-5 mm
Perineural infiltration	Surgical excision	Postsurgical or adjuvant radiotherapy, as necessary	≥5 mm	≥3 mm

¹ To be used by a physician with adequate expertise in the technique, using it for long enough for the margins to thaw in 1 min.

² PDT twice at an interval of 1-2 weeks. Photosensitizing methyl aminolevulinate ointment is applied to the skin. After letting the ointment work for 3 h, the area is subjected to red light (wavelength 630 nm) for about 8 min. The ointment and the light work together to cause a chemical reaction leading to the destruction of tumour cells.

³ Imiquimod (5%) five days a week for 4-6 weeks, until a crust reaction occurs, or fluorouracil (5%, may require special permit) twice daily for 3-4 weeks until crust reaction.

CO₂ = carbon dioxide; ED = electrodessication (electric peeling); PDT = photodynamic or light activation treatment

Non-surgical treatments

See Table T1.
Small superficial BCCs (e.g. < 0.5 cm on the face, < 1.5 cm on the trunk or upper limbs) can be treated with liquid nitrogen by a physician with adequate expertise in the technique (picture 8).
On lower limbs, cryotherapy of BCC is usually avoided due to the risk of leg ulcer.
For nodular BCC, surgery is the first-line option but freezing can also be used (image series 9, video Intense Cryotherapy of Superficial Basal Cell Carcinoma on the Back - Video), as considered appropriate. A light scar will remain.
Other non-surgical treatments for superficial BCC include photodynamic treatment (PDT) and treatment with imiquimod ointment.

Follow-up and risk of recurrence

No follow-up is generally needed for BCC removed with sufficient histological margins.
For high-grade or non-surgically treated BCC, follow-up should be planned in the treating unit, as considered appropriate.
About 1 in 3 patients with BCC will develop one or more BCCs over the next 3 years.
The risk of recurrence depends on the histological type of growth (Table T2) and individual risk factors, such as:
- large size of tumour
- indistinct margins
- previous recurrence
- immunosuppressive medication
- location at a site previously subjected to radiotherapy
- perineural infiltration.

Risk of recurrence of basal cell carcinoma according to histological type of growth (WHO Classification of Skin Tumours, 2018 http://publications.iarc.fr/Book-And-Report-Series/Who-Classification-Of-Tumours/WHO-Classification-Of-Skin-Tumours-2018). Source: Source: Hernberg M, Ilmonen S, Juteau S, Jääskeläinen A-S, Koljonen V, et al. Finnish guideline for the treatment of non-melanoma skin cancers. Duodecim Publishing Company 2020.

Low-grade BCC	High-grade BCC
Superficial	Infiltrating
Fibroepithelioma or Pinkus tumour	Sclerosing (morpheaform)
Nodular	Micronodular
Pigmented	Basosquamous
Infundibular cystic	Sarcomatoid

Specialist consultation

BCCs in difficult to treat areas, and high-grade BCCs, e.g. in the vicinity of eyelids, nostrils and ear canals.

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