Dark skin focalities: Difference between revisions

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[[File:Dark skin focalities.jpg|thumb|Dark skin focalities (in this case, from top left and clockwise: Spitz nevus, seborrheic keratosis, elevated melanocytic nevus and melanoma)]]
[[File:Dark skin focalities.jpg|thumb|Dark skin focalities (in this case, from top left and clockwise: Spitz nevus, seborrheic keratosis, elevated melanocytic nevus and melanoma)]]
Skin with one or more areas that are darker than the surroundings.
Skin with one or more areas that are darker than the surroundings. They are part of '''[[suspected malignant skin excisions]]'''.
 
{{Fixation - standard}}
==Fixation==
{{Fixation - general notes}}
{{Skin fixation, minimal}}
{{Gross processing of skin excisions}}


==Microscopic evaluation==
==Microscopic evaluation==
[[File:Pie chart of incidence and malignancy of pigmented skin lesions.png|thumb|370px|Various diagnoses of pigmented skin lesions, by relative incidence upon biopsy, and malignancy potential.]]
[[File:Pie chart of incidence and malignancy of pigmented skin lesions.png|thumb|370px|Various diagnoses of pigmented skin lesions, by relative incidence upon biopsy, and malignancy potential.]]
Evaluation is largely based on the relative incidence and malignancy of various differential diagnoses (see pie chart). Main approaches are:
*Direct pattern recognition
*Systematic


===Pattern recognition===
===Melanocytic lesions===
<gallery>
Scrolling through the epidermis at intermediate magnification and then through the dermis at a lower magnification.
File:Histopathology of melanocytic nevus.jpg|link=Melanocytic nevus|[[Melanocytic nevus]]
 
File:Histopathology of melanoma, HE.jpg|link=Melanoma|[[Melanoma]]
Melanocytic lesions (including nevus) are the most common, and can be classified as follows:
File:Blue nevus (4 of 4) (2797064219).jpg|link=Blue nevus|[[Blue nevus]]
{|class="wikitable"
!  !!colspan=2| Atypia and/or dysplasia
|-
!  !! Low !! High
|-
! Junction<br>between<br>epidermis<br>and dermis
| [[File:Histopathology of melanocytic nevus.jpg|link=Junctional nevus|200px|center]] '''[[Junctional nevus]]''' || [[File:Histopathology of lentigo maligna.jpg|200px|center|link=Melanoma in situ]] '''[[Melanoma in situ]]'''
|-
! Dermis
| [[File:Histopathology of dermal nevus, high magnification.jpg|160px|center|link=Dermal nevus]] '''[[Dermal nevus]]''' || [[File:Histopathology of nodular melanoma, high magnification.jpg|200px|center|link=Invasive melanoma of the skin]] '''[[Invasive melanoma of the skin|Invasive melanoma]]'''
|}
A '''compound nevus''' consists of both junctional and dermal melanocytic nevus nests.
 
===Non-melanocytic===
<gallery mode=packed heights=180>
File:Histopathology of a pigmented basal-cell carcinoma.jpg|Pigmented '''[[basal-cell carcinoma]]''', with palisading cells around nests.
File:Histopathology of seborrheic keratosis.jpg|link=Seborrheic keratosis|[[Seborrheic keratosis]]
File:Histopathology of seborrheic keratosis.jpg|link=Seborrheic keratosis|[[Seborrheic keratosis]]
File:Basal Cell Carcinoma, Nodular Pattern (6032028849).jpg|link=Basal cell carcinoma|[[Basal cell carcinoma]]
</gallery>
</gallery>
===Systematic===
By their relative incidences, one practical approach is:
*Is it a '''[[Dysplastic nevus|dysplastic (melanocytic) nevus]]'''? If not:
*Is it a '''[[Melanoma]]'''? If not:
*Compare to patterns of various other possibilities.
{{Bottom}}
{{Bottom}}
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