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Reading
1. Handbook of Dermoscopy - Chapter 2, Chapter 3 Sections 3b and 3d.
2. An Atlas of Surface Microscopy of Pigmented Skin Lesions: Dermoscopy – Chapter 7 and Chapter 6.
This module will introduce the 2 Step Dermoscopy Algorithm and then focus on the many and varied dermoscopic appearances of BCC and its simulators, as well as haemangioma and other common vascular lesions.
The 2 Step Dermoscopy Algorithm 1 is well described in both texts. Figure 2.1 in the Handbook of Dermoscopy is a concise summary and it would be useful to have this or a copy of it handy in your consulting room.
Whilst the first step is described as differentiating melanocytic lesions from non melanocytic lesions, in reality the presence of absence of a melanocytic proliferation is a histological feature not a dermoscopic one. This step can be viewed as sorting lesions that can diagnosed from the evident dermoscopic features such as BCC, haemangoima, Dermatofibroma, Solar lentigo etc, from those that could potentially be melanomas. In fact any lesion that cannot be diagnosed specifically in step one is considered by default to be melanocytic, not just those showing the defining features of a melanocytic lesion, and hence the second step (application of a melanocytic algorithm) is required. There are also many lesions that defy the first step, and are listed as exceptions below 2.
The defining features of a melanocytic lesion are:
1.Pigment network / reticulation - nevi / melanoma (exceptions : solar lentigo, reticulate seborrhoeic keratosis, ink spot lentigo, dermatofibroma, and accessory nipple)
2.Pseudo- network – Facial lesions (pseudo network also occurs in non melanocytic lesions e.g. solar lentigo)
3.Aggregated brown or black globules – nevi melanoma (exceptions: Seborrhoeic keratosis, dermatofibroma, subcorneal hemorrhage, basal cell carcinoma, cutaneous metastases)
4.Streaks - Spitz/ Reed Nevus, Melanoma (exceptions Seborrhoeic keratosis, basal cell carcinoma)
5.Homogeneous blue pigmentation – blue nevus, metastatic melanoma ( exceptions haemangioma/ angiokeratoma, Kaposi sarcoma, radiation tattoo, basal cell carcinoma)
6.Parallel pattern – acral lesions
References
1. Argentziano. G. et al 1: Dermoscopy of pigmented skin lesions: results of a consensus meeting via the Internet. J Am Acad Dermatol. 2003 May;48(5):679-93. See especially Appendix 1.
2. Scope. A. et al Nonmelanocytic lesions defying the two-step dermoscopy algorithm.
Dermatol Surg. 2006 Nov;3(11):1398-406.
Example 1. This lesion is an acanthotic type of seborrhoeic keratosis; it has features that resemble streaks but is not melanocytic. Note the sharply demarcated border and "stuck on" appearance of the clinical image.
Example 2. This is a dermatofibroma with central brown globules, but is not melanocytic.
Example 3. This ink spot lentigo shows a clear reticular network but is a non melanocytic lesion.
Example 4.This lesion on the back of an outdoors worker shows fine reticulation in areas appearing like fingerprint structures, such patterns often cover vast areas of sun damaged skin. There are some brown dots and central poorly defined blue areas. A shave biopsy of this lesion showed solar lentigo only and hence it is non melanocytic.
Example 5.This lesion also occurred on the sun damaged skin of an outdoors worker. A fine reticular pattern is noted. There are some poorly defined blue grey areas at 7 o’clock. This lesion was reported as a mildly dysplastic junctional nevus, that is a melanocytic lesion. There is little to differentiate this lesion from the previous example, an issue discussed in depth in the next module.
In 2000 Menzies et al 3 set out the dermoscopic features of pigmented BCC. A panel of experts confirmed the criteria in 2003 1 . They are illustrated and described in Table 3.2 of the Handbook of Dermoscopy
Whilst the primary role of dermoscopy in relation to BCC is differentiating pigmented BCC from Melanoma, in day to day practice dermoscopy is very useful for identifying BCC amongst the variety of lesions that are encountered. It is a particularly useful aid to identification of BCC’s when they are small and subtle and may otherwise be missed. Dermoscopy may also be helpful in determining the sub type of BCC and as an aid to defining the extent of the lesion.
Notes on dermoscopic features of BCC
Pigmented BCC are said to account for between 5-7 percent of all BCC in white skinned populations. Nodular variants of BCC are the most common to show significant pigmentation, followed by the superficial multifocal variant. Pigmentation can occur in other types of BCC but is uncommon.
Where a BCC occurs on sun damaged skin the reticular pigmentation of lentigo may exist in close association with the lesion.
Regression structures including fine peppering leading to a “dirty dish water appearance” can occur in BCC but are not included in the specific criteria. White scar like areas are also quite common especially in the superficial multifocal, infiltrating and morphaic types.
The Aborising Vessels in BCC are sharply focused vessels with distinct “tree-like” branching. Other types of vessels may occur in BCC including glomerular, hairpin and linear irregular types but they are not diagnostic.
Dark brown pigmentation is less common in pigmented BCC than nevi and melanoma. Two thirds of pigmented BCC have pigmentation occupying less than 50% of the lesion and only 7% of lesions have pigmentation occupying greater than 75% of the lesion.
A study of inter observer agreement on the diagnostic criteria for BCC showed good or satisfactory concordance for absence of pigment network, ulcerations, aborising vessels, spoke-wheel areas and multiple blue grey globules. Concordance for large blue grey ovoid nests was surprisingly poor, and the poorest concordance was perhaps not surprisingly for leaf like areas 4 .
Histopathologic correlation of the dermoscopic features have been studied and the main correlates are listed below 5 .
Large grey-blue ovoid nests: melanin-containing cells in papillary or reticular dermis
Leaf-like areas: pigmented epithelial nests in papillary dermis
Multiple grey-blue globules: melanin-containing cell nests in dermis
Aborising telangiectasia: dilated vessels in dermis
Whilst most of the published literature relates to pigmented BCC, a recent pilot study by Giacomel and Zalaudek 6 reviewed a series of superficial BCC. For this sub type they described all lesions as showing a shiny white to red appearance. Whilst only a few lesions had typical aborising vasculature, 90% showed irregularly dispersed, short, fine telangiectasias (SFTs), and 70% showed multiple fine ulcerations. Of note the clinical diagnosis was correct in less than half of cases with Solar Keratosis, Bowen’s disease and other sub types of BCC being the most frequent misdiagnoses.
Dermoscopy can help outline the margins of BCC. The typical aborising vessels differ from the telangiectasia seen on sun damaged skin and the shiny white to red areas differ from the background skin. A study by Ralph Braun ( with cases contributed by Peter Bourne) comparing dermoscopically measured margins with histologically measured margins is pending publication.
Non neoplastic lesions can mimic BCC as well common examples being guttate psoriasis and purigo nodularis.
Rererences
3. Menzies, S.W. et al. Surface microscopy of pigmented basal cell carcinoma. Arch Dermatol. 2000 Aug;136(8):1012-6.
4: Peris, K. et al. Interobserver agreement on dermoscopic features of pigmented basal cell carcinoma. Dermatol Surg. 2002 Jul;28(7):643-5.
5. Demirtasoglu, M. et al. Evaluation of dermoscopic and histopathologic features and their correlations in pigmented basal cell carcinomas. J Eur Acad Dermatol Venereol. 2006 Sep;20(8):916-20.
6 : Giacomel J & Zalaudek I. Dermoscopy of superficial basal cell carcinoma.
Dermatol Surg. 2005 Dec;31(12):1710-3.
Example 6. This is a nodulo-cystic BCC arising in sun damaged lentiginous skin showing a large blue grey ovoid nest, and fine aborising vessels. The surrounding skin shows reticulation and some fingerprinting typical of solar lentigo.
Example 7. This lesion could be mistaken for a BCC but is actually sebaceous gland hyperplasia. It was one of a crop of similar lesions on the forehead and cheeks of a male patient. A couple of the vessels show single branching but are not sharply focused, they do no cross the center of the lesion as typically seen in BCC. These are referred to as crown vessels they have a wreath like arrangement; the lobular patten of the cystic areas also favors sebaceous hyperplasia. If there is doubt a biopsy will settle the question.
Example 8.. This lesion is nodular BCC showing multiple subtle leaf like areas , a few subtle blue gray globules and a network of fine aborising vessels which typically course over the edges of the lesion and may cross the center. Milia like cysts can occur in BCC’s and on occasions will be multiple they are of no diagnostic relevance.
Have a look at this case study.
and then
Please Proceed the next part Module 2.2
