View source for Melanoma in situ

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|author1=[[User:Mikael Häggström|Mikael Häggström]]
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Melanoma of the [[skin]] generally presents as a '''[[Dark skin focalities|dark skin focality]]''' and/or a '''[[suspected malignant skin excision]]'''.
{{Fixation - standard}}
{{Fixation - general notes}}
==Gross processing==
{{Basic gross evaluation of suspected malignant skin lesions}}
{{Tissue selection from suspected malignant skin lesions}}

==Microscopic evaluation==

===Differential diagnoses===
Distinguish mainly from '''[[dysplastic nevus]]''' and '''[[invasive melanoma of the skin]]''':
====Dysplastic nevus====
{{Table comparing congenital nevus, dysplastic nevus and suspected melanoma}}

{{Evaluation of suspected malignancies}}

====Invasive melanoma of the skin====
'''[[Invasive melanoma of the skin]]''' has features melanoma in situ, but also has dermal involvement of atypical melanocytes with cytologic atypia and no maturation.<ref>{{cite web|url=http://www.pathologyoutlines.com/topic/skintumormelanocyticmelanoma.html|title=Skin melanocytic tumor - Melanoma - Invasive melanoma|author=Christopher S. Hale|website=Pathology Outlines}} Topic Completed: 1 May 2013. Revised: 17 September 2019</ref>

===Further workup===
Upon a diagnosis of melanoma ''in situ'', evaluate its margins.<br>Optionally, attempt to determine the histopathologic type and amount of cytoplasmic pigmentation:

;Margins
If melanoma, determine if the distance to any margin is greater or lesser than 2-3 mm. 
*2 mm is used as a cutoff for sharply demarcated, small, superficially spreading or nevoid melanomas.<ref name=busam2018>Measurements used to classify a melanoma as radical: [https://books.google.se/books?id=oepmDwAAQBAJ&pg=PA406 Page 406] in: {{cite book|title=Pathology of Melanocytic Tumors|author=Klaus J. Busam, Richard A Scolyer, Pedram Gerami|publisher=Elsevier Health Sciences|year=2018|isbn=9780323508681}}</ref>
*3 mm is used for ill-defined lentigo maligna melanoma in situ.<ref name=busam2018/>
If lesser, quantify the distance.

If margins are '''difficult to determine''', consider immunohistochemistry with SOX10 to better visualize melanoma nests.<ref group="note" name="SOX10"/>

;Histopathologic type
Main types of melanoma ''in situ'' are:

{|class="wikitable"
! Type !! Features !! Micrograph
|-
! Superficial spreading melanoma ''in situ''
| Melanoma cells with nest formation along the dermo-epidermal junction.
| [[File:Histopathology of superficial spreading melanoma.jpg|190px]]
|-
! Lentigo maligna
| Linear spread of atypical epidermal melanocytes along stratum basale.<ref name=DermNet>{{cite web|url=https://dermnetnz.org/topics/lentigo-maligna-and-lentigo-maligna-melanoma/|author=Hon A/Prof Amanda Oakley|year=2011|website=DermNet NZ}}</ref>
| [[File:Histopathology of lentigo maligna.jpg|center|190px]]
|-
! Acral lentiginous melanoma ''in situ''
| Continuous proliferation of atypical melanocytes at the dermoepidermal junction.<ref name="Piliang2009">{{cite journal|last1=Piliang|first1=Melissa Peck|title=Acral Lentiginous Melanoma|journal=Surgical Pathology Clinics|volume=2|issue=3|year=2009|pages=535–541|issn=18759181|doi=10.1016/j.path.2009.08.005}}</ref>
| [[File:Histopathology of acral lentiginous melanoma in situ, intermediate magnification.jpg|190px]]
|}

==Report==
Most important entries:
*Melanoma '''area''' dimensions (width x width)<ref name=melanoma>{{cite web|url=https://www.aimatmelanoma.org/diagnosing-melanoma/pathology/example-melanoma-pathology-report/|title=An Example of a Melanoma Pathology Report|website=Melanoma Foundation|accessdate=2019-09-24}}</ref>
{{Skin radicality report|include-ref=<ref name=melanoma/>|margin=2 or 3|margin-comment=as per [[#Further workup|Further workup]] above}}
{{Reporting}}
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