Introduction to the top-down 2-step approach

From dermoscopedia

Main PageTwo-step algorithmIntroduction to the top-down 2-step approach
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 Authored by: Ralph P. Braun     ·  Ashfaq A. Marghoob     ·  Aimilios Lallas

 Keywords:   two-step algorithm
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Description This chapter describes the principleThis glossary term has not yet been described. of the 2 step algorithmIn mathematics and computer science, an algorithm (Listeni/ˈælɡərɪðəm/ AL-gə-ri-dhəm) is a self-contained sequence of actions to be performed. Algorithms can perform calculation, data processing and automated reasoning tasks.
Author(s) Ralph P. Braun · Ashfaq A. Marghoob · Aimilios Lallas
Responsible author Ash Marghoob→ send e-mail
Status released
Status update July 2, 2018
Status by Ralph P. Braun


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The top-down 2-step pattern analysisThis glossary term has not yet been described. approach builds upon the previous classic [1] and revised [2] 2-step approaches by eliminating the requirement to differentiate melanocyticThis glossary term has not yet been described. from non-melanocytic lesions in step 1. This algorithm hinges on the concept that the observer’s diagnostic accuracyThis glossary term has not yet been described. for skin cancerThis glossary term has not yet been described., specifically melanomaThis glossary term has not yet been described., is, metaphorically, like a two-sided coin. One side of the coin requires the observer to make a specific diagnosisis the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines with variations in the use of logic, analytics, and experience to determine "cause and effect". In systems engineering and computer science, it is typically used to determine the causes of symptoms, mitigations, and solutions by recognizing the classic patternsThis glossary term has not yet been described./structuresThis glossary term has not yet been described. associated with neviThis glossary term has not yet been described., dermatofibromas (DF), intradermal neviThis glossary term has not yet been described. (IDNThis glossary term has not yet been described.), basal cell carcinomas (BCCAbbreviation for Basal Cell Carcinoma), squamous cell carcinomas (SCCThis glossary term has not yet been described.), lentigines & seborrheic keratosesThis glossary term has not yet been described. (SK), angiomas, angiokeratomas, sebaceous hyperplasias, and clear cell acanthoma(also known as "Acanthome cellules claires of Degos and Civatte," "Degos acanthoma," and "Pale cell acanthoma") is a benign clinical and histological lesion initially described as neoplastic, which some authors now regard as a reactive dermatosis. It usually presents as a moist solitary firm, brown-red, well-circumscribed, 5 mm to 2 cm nodule or plaque on the lower extremities of middle-aged to elderly individuals The lesion has a crusted, scaly peripheral collarette and vascular puncta on the surface. It is characterized by slow growth, and may persist for years. The clinical differential diagnosis includes: dermatofibroma, inflamed seborrheic keratosis, pyogenic granuloma, basal cell carcinoma, squamous cell carcinoma, verruca vulgaris, psoriatic plaque, and melanoma. (CCA). Needless to say, the individual dermoscopic structuresThis glossary term has not yet been described. present in a lesion, within each diagnostic category (nevusThis glossary term has not yet been described., DF, BCC, etc), need to be placed within the contextThis glossary term has not yet been described. of the other features within the lesion. In other words, the global pattern defining a specific diagnosis is defined by the presence of distinct structures that have previously been found to carry a high predictive value for that specific diagnosis.

The other side of the coin requires the observer to acknowledge the nevus patterns that require context for their interpretation and the patterns and structures associated with melanoma. Armed with a clinical differential diagnosis followed by evaluation of the lesion via this top-down 2-step approach can facilitate the rendering of an accurate diagnosis or at least guide the clinician towards the most appropriate managementThis glossary term has not yet been described. plan.

In a simplified way, the main queries of the top-down 2-step analysis are: Step-1: To establish a specific diagnosis (if possible) Step-2: To rule out melanoma



ReferencesThis is material contained in a footnote or bibliography holding further information.
  1. Argenziano et al.: DermoscopyThe examination of [skin lesions] with a 'dermatoscope'. This traditionally consists of a magnifier (typically x10), a non-polarised light source, a transparent plate and a liquid medium between the instrument and the skin, and allows inspection of skin lesions unobstructed by skin surface reflections. Modern dermatoscopes dispense with the use of liquid medium and instead use polarised light to cancel out skin surface reflections. of pigmented skin lesions: results of a consensus meeting via the Internet. J. Am. Acad. Dermatol. 2003;48:679-93. PMID: 12734496. DOI.
  2. Marghoob & Braun: Proposal for a revised 2-step algorithm for the classificationis a general process related to categorization, the process in which ideas and objects are recognized, differentiated, and understood. of lesions of the skin using dermoscopyThe examination of [skin lesions] with a 'dermatoscope'. This traditionally consists of a magnifier (typically x10), a non-polarised light source, a transparent plate and a liquid medium between the instrument and the skin, and allows inspection of skin lesions unobstructed by skin surface reflections. Modern dermatoscopes dispense with the use of liquid medium and instead use polarised light to cancel out skin surface reflections.. Arch Dermatol 2010;146:426-8. PMID: 20404234. DOI.