Streaks

From dermoscopedia

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 Editor: Ralph P. Braun

 Author(s): Ralph P. Braun     ·  Katrin Kerl
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Description In this chapter we describe streakslines radial (always at periphery) streaks Reed nevus melanoma recurrent nevus also calles Pseudopods and radial streamingRadial linear extensions at the lesion edge and their histopathological correlation
Author(s) Ralph P. Braun · Katrin Kerl
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Status update July 27, 2017
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Streakslines radial (always at periphery) streaks Reed nevus melanoma recurrent nevus are linear pigmented projections seen at the periphery of lesions.
Streaks schematic 25.jpg
Both pseudopods (streaks with bulbous projections at their tips) and radial streaming (streaks without bulbous projections at their tips) are considered to be streaks. Streaks in melanomaThis glossary term has not yet been described. are usually observed only focally and asymmetrically at the lesion’s periphery and refl ect the radial growth phase of the tumor. On the other hand, streaks that are distributed symmetrically around the entire perimeter of the lesion are seen mostly in pigmented spindle cell neviThis glossary term has not yet been described. (Spitz or Reed). Histologically, streaks represent confluent junctional nests of melanocytes. Pseudopods are finger-like projections of dark pigment (brown to black) at the periphery of the lesion. They have small knobs at their tips, and are connected to either a central pigment networkThis glossary term has not yet been described. or central pigmented blotchDark structureless areas. To be considered pseudopods the bulbous knobs must have a maximum diameter that is larger than the network from which it originates. Menzies and colleagues found pseudopods to be one of the most specific features of superficially spreadingThis glossary term has not yet been described. melanoma. On histopathologyThis glossary term has not yet been described., pseudopods correspond to junctional confluent nests of melanocytes at the periphery of the lesion. Confluence of nests is also a criterion in histopathology, typical for dysplastic neviThis glossary term has not yet been described. or malignant melanoma. Depending on which area of the pseudopod is sectioned on histologyThis glossary term has not yet been described., the pathologist will see this structure either as a circular cluster of cells of varying diameters or as an oval-shaped cluster of cells. Only if the pathologyThis glossary term has not yet been described. section passes exactly through the longitudinal axis of a pseudopod will the pathologist be able to recognize this structure as an elongated tubular cluster of cells.
Pseudopod histology.jpg

Needless to say, the statistical probability of this happening is very low unless of course the pathologist uses 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. at the grossing table to orient and oversee the step sectioning process. On occasion, peripheral globulesThis glossary term has not yet been described. and pseudopods can look similar to each other at first glance. However, with peripheral globules one will observe a small clear space separating the globuleThis glossary term has not yet been described. from the main tumor mass.

These peripheral globules are presumed to correspond to junctional melanocyticThis glossary term has not yet been described. nests at the tips of rete ridgesEpidermal extensions that project into the underlying dermis and they are usually associated with growing/enlarging nevi. In contrast, pseudopods emanatefrom, and are directly connected to, the main tumor mass through a stalk. Radial streamingRadial linear extensions at the lesion edge appears as radial parallel linear extensions at the periphery of the lesion. On histopathology, radial streaming also correlates with confluent junctional nests of pigmented melanocytes.
Regular streaks.jpg
Irregular pseudopods .jpg