Basal Cell Carcinoma

Author: Dr Charlotte Michelmore

Chief Editor: Dr Daniel Keith

Introduction

Basal Cell Carcinoma (BCC), aka ‘rodent’ ulcer, is the most common type of skin cancer, accounting for approximately 80% of non-melanoma skin cancers. BCCs primarily affect sun-exposed areas of the skin, particularly the face, trunk, and limbs. Although they are generally slow-growing and rarely metastasize, early detection and treatment is crucial as they can be locally invasive and destructive leading to complications and surgical disfigurement.

The four main types of BCC are nodular, superficial, morphoeic (also known as sclerosing or infiltrative) and basosquamous. Each type can be pigmented or non-pigmented, the latter being much more common. Treatment includes local excision, curettage and cautery, mohs micrographic surgery, cryotherapy, topical creams (imiquimod cream and 5-fluorouracil cream), radiotherapy and photodynamic therapy.

It can be difficult to distinguish BCCs from other benign skin lesions, such as seborrheic keratosis, intradermal naevus, and benign adnexal tumours. Some heavily pigmented BCCs can be mistaken as melanomas. The following dermoscopic features are indicative of BCCs and can aid in their diagnosis.

(NB although these features are indicative of BCC they are not diagnostic without exception and can all be seen in other skin cancers and benign lesions, and so clinical-dermoscopic correlation is imperative. A suspected BCC should still be managed as a potentially more aggressive tumor if the history suggests one (eg rapid growth), and a diagnosis of BCC should not rest on dermoscopy alone).

Dermoscopic Features

Arborising Telangiectasia

Arborising Telangiectasia are dilated, branching blood vessels that resemble the branches of a tree or the limbs of a spider. The branches radiate from a central point and tend to be asymmetrical. They can range in colour from light red to dark red, or even red-blue, and are often sharpy in focus when viewed with a dermatoscope. Arborising blood vessels are typical of nodular BCCs and represent neovascularisation in the dermis.

NB If polymorphic vessels (multiple different types of blood vessels) are present in one lesion, amelanotic melanoma must be ruled out.

Short, Fine Telangiectasia

In contrast to the arborising type, these are very short, sharply focused segments of telangiectasia with few branches and are typical of superficial BCCs.

Atypical vessels

Unusual vessel shapes may be seen including commas, dots, corkscrewing and ‘M’ vessel linkages.

Multiple Colours

Some BCCs exhibit more than one colour under dermoscopy. This multifocal colour pattern, such as brown, black, red, or blue areas, can be indicative of an aggressive or infiltrative lesion.

Ulceration

Ulcers appear as large structureless orange-red areas, whereas erosions are smaller areas of yellow-orange or reddish-brown. They can be multiple and vary in size. Ulceration and erosions are seen in superficial and nodular BCCs.

Blue-Grey Structures

BCCs can demonstrate several blue-grey structures such as ovoid nests, globules and dots. Blue-grey ovoid nests are well-defined collections of melanin that are typically round or oval-shaped. They can be numerous and occasionally confluent. Nests that are blue in colour are characteristic of deeper, more aggressive, nodular BCCs. Globules are smaller than nests and are usually discrete. Dots are the smallest blue-grey structure and can appear like ‘peppering’ under the dermatoscope

White globules

These appear as white, light pink or yellow areas and can be arranged in clusters. On histology, dystrophic calcification is seen.

Shiny white structures

These are ill-defined shiny areas or streaks of white or red that can look like a scar. This is seen where there is diffuse fibrosis of the dermis.

NB These shiny white lines are only visible in polarised dermoscopy!

Spoke-Wheel and Concentric Structures

Spoke-wheel structures resemble the spokes of a bike wheel with light brown projections arising from a darker coloured centre. Concentric structures are less defined and appear globular with a dark centre. They are also commonly seen in superficial BCCs.

Leaf-like Structures

Leaf-like structures are light brown pigmented blobs that converge to look like a maple leaf or leaves. They often have blurred borders and are located at the periphery of the lesion. These are commonly seen in superficial BCCs