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Melanocytic lesions (view source)

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'''Melanocytic lesions''' are commonly encountered in [[dermatopathology]] and an area which causes some difficulty, i.e. it is hard to decide in some cases whether a lesion is benign (e.g. Spitz nevus) or malignant ([[malignant melanoma]]).
[[Image:Blue nevus - intermed mag.jpg|thumb|right|A melanocytic lesion ([[blue nevus]]). [[H&E stain]]. (WC/Nephron)]]
'''Melanocytic lesions''' are commonly encountered in [[dermatopathology]] and an area which causes some difficulty, i.e. it is hard to decide in some cases whether a lesion is benign (e.g. [[Spitz nevus]]) or malignant ([[malignant melanoma]]).


==Overview==
=Overview=
===Identifying melanocytes===
===Identifying melanocytes===
*Clear ''or'' pigmented cytoplasm.
*Clear ''or'' pigmented cytoplasm.
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| Children & adolescents
| Children & adolescents
| usu. non-pigmented
| usu. non-pigmented
| [http://www.drmihm.com/cases/casefigure.cfm?figID=931&CaseID=51 Spitz nevus (drmihm.com)]
| [http://www.drmihm.com/cases/casefigure.cfm?figID=931&CaseID=51 Spitz nevus (drmihm.com)], [http://commons.wikimedia.org/wiki/File:Spitz_nevus_-_high_mag.jpg Spitz nevus - high mag. (WC)], [http://commons.wikimedia.org/wiki/File:Spitz_nevus_-_intermed_mag.jpg Spitz nevus - intermed. mag. (WC)]
| <ref name=Ref_WMSP499>{{Ref WMSP|499}}</ref>
| <ref name=Ref_WMSP499>{{Ref WMSP|499}}</ref>
|-
|-
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| may be familial - precursor to melanoma
| may be familial - precursor to melanoma
| may have asymmetry in shape or pigmentation
| may have asymmetry in shape or pigmentation
| [http://commons.wikimedia.org/wiki/File:Dysplastic_nevus_-_low_mag.jpg Dysplastic nevus - low mag.], [http://commons.wikimedia.org/wiki/File:Dysplastic_nevus_-_add_-_high_mag.jpg Dysplastic nevus - high mag.]
| [http://commons.wikimedia.org/wiki/File:Dysplastic_nevus_-_low_mag.jpg Dysplastic nevus - low mag.], [http://commons.wikimedia.org/wiki/File:Dysplastic_nevus_-_add_-_high_mag.jpg Dysplastic nevus - high mag.]  
| <ref name=Ref_WMSP502>{{Ref WMSP|502}}</ref>
| <ref name=Ref_WMSP502>{{Ref WMSP|502}}</ref>
|-
|-
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*"Maturation" in the context of melanocytic lesions ''means'' (1) the cells get smaller with depth, (2) cells are less mitotic with depth.
*"Maturation" in the context of melanocytic lesions ''means'' (1) the cells get smaller with depth, (2) cells are less mitotic with depth.


==Melanocytic nevus==
=Lentiginous melanocytic lesions=
==Lentigo simplex==
{{Main|Lentigo simplex}}
 
==Solar lentigo==
*Plural ''solar lentigines''.
===General===
*Benign.
 
Fits into the larger category of ''lentiginous melanocytic proliferations'' - these include:<ref name=Ref_Derm438>{{Ref Derm|438}}</ref>
*Solar lentigo.
*[[Lentigo simplex]].
*Lentiginous nevus.
*Lentiginous [[melanoma in situ]].
 
===Gross===
Features:<ref name=Ref_Derm438>{{Ref Derm|438}}</ref>
*Small (< 4 mm), irregular brown [[macule]].
*Usu. sun-exposed area.
 
DDx (clinical):
*[[Lentigo maligna]] - melanoma in situ on sun damaged skin.
*[[Seborrheic keratosis]], flat.<ref name=dermammin_sl>URL: [http://www.dermaamin.com/site/histopathology-of-the-skin/53-a/1555-actinic-lentigo-.html http://www.dermaamin.com/site/histopathology-of-the-skin/53-a/1555-actinic-lentigo-.html]. Accessed on: 6 May 2013.</ref>
 
===Microscopic===
Features:<ref name=Ref_Derm437>{{Ref Derm|437}}</ref>
*Hyperpigmented melanocytes - may be present in increased quantities - '''key feature'''.
**Classically at the tips of the rete ridges.
*No (melanocyte) nuclear atypia.
*Solar damage ([[solar elastosis]]).<ref name=pmid19536147>{{Cite journal  | last1 = Hafner | first1 = C. | last2 = Stoehr | first2 = R. | last3 = van Oers | first3 = JM. | last4 = Zwarthoff | first4 = EC. | last5 = Hofstaedter | first5 = F. | last6 = Klein | first6 = C. | last7 = Landthaler | first7 = M. | last8 = Hartmann | first8 = A. | last9 = Vogt | first9 = T. | title = The absence of BRAF, FGFR3, and PIK3CA mutations differentiates lentigo simplex from melanocytic nevus and solar lentigo. | journal = J Invest Dermatol | volume = 129 | issue = 11 | pages = 2730-5 | month = Nov | year = 2009 | doi = 10.1038/jid.2009.146 | PMID = 19536147 }}</ref>
 
Notes:
*Should ''not'' be present:<ref name=Ref_Derm438>{{Ref Derm|438}}</ref>
**Nests of melanocytes.
**Pagetoid spread of melanocytes.
 
DDx:<ref name=Ref_Derm437>{{Ref Derm|437}}</ref>
*Pigmented [[actinic keratosis]].
*[[Lichen planus-like keratosis]].
*Pigmented [[seborrheic keratosis]].
*[[Ephelis]] (freckle).
 
====Images====
<gallery>
Image:Skin_tumors_181.jpg | Solar lentigo. (WC)
</gallery>
*[http://www.dermaamin.com/site/images/histo-pic/a/actinic-lentigo/actinic-lentigo1.jpg Solar lentigo (dermammin.com)].<ref name=dermammin_sl>URL: [http://www.dermaamin.com/site/histopathology-of-the-skin/53-a/1555-actinic-lentigo-.html http://www.dermaamin.com/site/histopathology-of-the-skin/53-a/1555-actinic-lentigo-.html]. Accessed on: 6 May 2013.</ref>
 
===Sign out===
<pre>
FOREARM LESION, RIGHT, PUNCH BIOPSY:
- SOLAR LENTIGO.
</pre>
 
====Micro====
The sections show hair-bearing skin with basilar pigmentation at the tips of the rete ridges and solar elastosis.  No melanocytic nests are identified.  The epidermal cells mature to the surface.  No significant inflammation is present.
 
==Lentiginous melanocytic nevus==
*[[AKA]] ''lentiginous nevus''.
===General===
===General===
*Benign.
*Benign.
*Think ''melanoma''.
 
Fits into the larger category of ''lentiginous melanocytic proliferations'' - these include:<ref name=Ref_Derm438>{{Ref Derm|438}}</ref>
*[[Solar lentigo]].
*[[Lentigo simplex]].
*Lentiginous nevus.
*Lentiginous [[melanoma in situ]].
 
===Gross===
*Small flat pigmented lesion.
 
===Microscopic===
Features:<ref name=Ref_Derm438>{{Ref Derm|438}}</ref>
*Melanocytes without atypia in the epidermis only - '''key feature'''.
*Melanocytic nests.
*+/-Rete ridge elongation.
 
DDx:
*[[Atypical lentiginous nevus]].
*[[Dysplastic nevus]].
*[[Melanoma in situ]] - especially if [[solar elastosis]] is present.
 
====Images====
www:
*[http://www.derm101.com/Popups/FigurePopup.aspx?id=dp0101a06f005&aid=740564&filename=dp0101a06g005b Lentiginous nevus (derm101.com)].
 
===Sign out===
<pre>
SKIN LESION, BACK, SHAVE EXCISION:
- JUNCTIONAL LENTIGINOUS NEVUS.
-- COMPLETELY EXCISED (LATERAL CLEARANCE 1 MM).
</pre>
 
====Micro====
The sections show skin with non-nested melanocytes in the epidermis. The melanocytes have no significant cytologic atypia. There is no upward scatter of melanocytes. The lesion is completely excised the in plane of section.
 
=Nested melanocytic lesions=
==Common melanocytic nevus==
*[[AKA]] ''common nevus''.
*In common language: ''mole''.
*In common language: ''mole''.
 
===General===
*Benign.
*Common.
*Think ''[[melanoma]]''.
Clinical:  
Clinical:  
*''ABCD'' = asymmetric, borders (irregular), colour (black), diameter (large).
*''ABCD'' = asymmetric, borders (irregular), colour (black), diameter (large).
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====Subtypes====
====Subtypes====
=====Compound melanocytic nevus=====
=====Compound melanocytic nevus=====
*Abbreviated ''CMN'' and ''CN''.
*In the dermis '''and''' epidermis - '''key feature'''.
*In the dermis '''and''' epidermis - '''key feature'''.


=====Junctional melanocytic nevus=====
=====Junctional melanocytic nevus=====
*Abbreviated ''JN''.
*In the epidermis - '''key feature'''.
*In the epidermis - '''key feature'''.


=====Intradermal melanocytic nevus=====
=====Intradermal melanocytic nevus=====
*[[AKA]] ''dermal nevus'', [[AKA]] ''intradermal melanocytic nevus''.
*[[AKA]] ''dermal nevus''.
*Only in the dermis - '''key feature'''.
*[[AKA]] ''intradermal melanocytic nevus''.
*[[AKA]] ''intradermal nevus'', abbreviated ''IDN''.<ref name=pmid11493376>{{Cite journal  | last1 = Fullen | first1 = DR. | last2 = Reed | first2 = JA. | last3 = Finnerty | first3 = B. | last4 = McNutt | first4 = NS. | title = S100A6 preferentially labels type C nevus cells and nevic corpuscles: additional support for Schwannian differentiation of intradermal nevi. | journal = J Cutan Pathol | volume = 28 | issue = 8 | pages = 393-9 | month = Sep | year = 2001 | doi =  | PMID = 11493376 }}</ref>
{{Main|Intradermal nevus}}


======Sign out======
===Sign out===
 
====Junctional melanocytic nevus====
<pre>
<pre>
SKIN, PUNCH BIOPSY:  
SKIN LESION, RIGHT LATERAL UPPER ARM, BIOPSY:
- INTRADERMAL MELANOCYTIC NEVUS.
- BENIGN JUNCTIONAL NEVUS.
</pre>
</pre>
=====Micro=====
The sections show melanocytes in nest confined to the epidermis. The lesion is symmetrical in its architecture and pigment distribution. There is no pagetoid spread of melanocytes in the epidermis. No significant nuclear atypia is identified. No mitotic activity is appreciated.
The lesion is completely excised in the plane of section.
====Compound melanocytic nevus====
{{Main|Compound nevus}}
====Intradermal melanocytic nevus====
{{Main|Intradermal nevus}}


==Congenital-pattern nevus==
==Congenital-pattern nevus==
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*Growth along dermal structures - '''key feature'''.
*Growth along dermal structures - '''key feature'''.
**Nerves, hair shafts, ducts.
**Nerves, hair shafts, ducts.
**"Deep" melanocytes.
*Lacks nuclear atypia.
*Lacks nuclear atypia.
*+/-Mitoses.
*+/-Mitoses.
*+/-Less nesting.<ref name=cong_nevus_dermpedia/>


==Recurrent nevus==
DDx:
*[[Intradermal melanocytic nevus]].
*[[Malignant melanoma]].
 
Images:
*[http://www.dermpedia.org/image/congenital-nevus-4 Congenital nevus - 4 (dermpedia.org)].<ref name=cong_nevus_dermpedia>URL: [http://www.dermpedia.org/dermpedia-textbook/congenital-nevus http://www.dermpedia.org/dermpedia-textbook/congenital-nevus]. Accessed on: 27 December 2012.</ref>
*[http://www.dermpedia.org/image/congenital-nevus-5 Congenital nevus - 5 (dermpedia.org)].
 
===Sign out===
<pre>
SKIN LESION, LEFT UPPER BACK, BIOPSY:
- COMPOUND MELANOCYTIC NEVUS WITH CONGENITAL FEATURES.
</pre>
 
==Recurrent melanocytic nevus==
*[[AKA]] ''persistent melanocytic nevus''.
*[[AKA]] ''pseudomelanoma''.
===General===
===General===
*Partially excised nevi. (???)
*Classically, arises at the site of a partially excised nevus.<ref name=Ref_Derm465>{{Ref Derm|465}}</ref>


===Microscopic===
===Microscopic===
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#Features of an [[intradermal nevus]].
#Features of an [[intradermal nevus]].


==Pigmented spindle cell nevus==
May have:<ref name=Ref_Derm465>{{Ref Derm|465}}</ref>
*[[AKA]] ''pigmented spindle cell nevus of Reed''.
*Pagetoid spread of melanocytes.
*Confluent nests at the DE junction.
*Nuclear atypia - uncommon.
 
DDx:<ref name=Ref_Derm465>{{Ref Derm|465}}</ref>
*[[Melanoma in situ]] - classically spread beyond the scar, unlike pseudomelanoma - growth confined to epidermis.
*[[Sclerosing nevus]].
 
===IHC===
*HMB-45 deep component -ve.
*Ki-67 - non-proliferative.
 
==Sclerosing melanocytic nevus==
*[[AKA]] ''sclerosing nevus''.


===General===
===General===
*Uncommon.
*Similar to ''[[recurrent nevus]]''.
*Women in teens & 20s.
*Clinically may be confused with [[melanoma]].
*Location: shoulder, pelvic girdle region.
*No history of trauma or prior excision.


===Microscopic===
===Microscopic===
Features:<ref name=Ref_WMSP500>{{Ref WMSP|500}}</ref>
Features:<ref name=pmid18537860 >{{Cite journal  | last1 = Fabrizi | first1 = G. | last2 = Pennacchia | first2 = I. | last3 = Pagliarello | first3 = C. | last4 = Massi | first4 = G. | title = Sclerosing nevus with pseudomelanomatous features. | journal = J Cutan Pathol | volume = 35 | issue = 11 | pages = 995-1002 | month = Nov | year = 2008 | doi = 10.1111/j.1600-0560.2007.00941.x | PMID = 18537860 }}</ref>
*Nests of heavily pigmented spindle cells at dermal-epidermal junction - '''key feature'''.
*Trizonal - may be described as a ''sandwich'':
**Nevoid cells in epidermis & dermis - form "basket weave" pattern
*# [[Junctional melanocytic nevus|Junctional]] ''or'' [[compound nevus]].
*Well-circumscribed lesion.
*#* May have pagetoid spread of melanocytes, i.e. non-basal melanocytes in the epidermis.
 
*#* Cannot have cytologic atypia - presence of cytologic atypia in this layer makes it [[melanoma]].
Notes:
*# Fibrotic tissue with irregular melanocytic nests.
*No epithelioid nevus cells.
*# Nevus below scar - may be [[common melanocytic nevus|common]], congenital-type, [[dysplastic nevus|dysplastic]], [[spitz nevus|Spitz]].


DDx:
DDx:
*[[Spitz nevus]].
*[[Malignant melanoma]].
*[[Melanoma]].
*[[Recurrent melanocytic nevus]] - also trizonal; however, has a fibrotic layer that does ''not'' have melanocytes in it.<ref name=pmid18537860 />


Images:
==Pigmented spindle cell nevus==
*[http://commons.wikimedia.org/wiki/File:Pigmented_spindle_cell_nevus_-_low_mag.jpg PSCN - low mag. (WC)]. *[http://commons.wikimedia.org/wiki/File:Pigmented_spindle_cell_nevus_-_2_-_intermed_mag.jpg PSCN - intermed. mag. (WC)]. *[http://www.histopathology-india.net/Reed.htm Reed nevus - collection (histopathology-india.net)].
*[[AKA]] ''pigmented spindle cell nevus of Reed''.
{{Main|Pigmented spindle cell nevus}}


==Spitz nevus==
==Spitz nevus==
*AKA ''epithelioid and spindle-cell nevus''.
*[[AKA]] ''epithelioid and spindle cell nevus''.
{{Main|Spitz nevus}}
 
==Acral nevus==
*[[AKA]] ''melanocytic nevus with intraepidermal ascent of cells'' ([[MANIAC]]).
*[[AKA]] ''volar nevus''.
{{Main|Acral nevus}}


===General===
==Dysplastic melanocytic nevus==
*May be very difficult to differentiate from [[melanoma]].
*[[AKA]] ''dysplastic nevus''.
*[[AKA]] ''Clark nevus''.
*[[AKA]] ''nevus with architectural disorder''.
**This term is recommended by the American NIH; however, it is not widely adopted.<ref name=pmid22703907>{{Cite journal  | last1 = Elston | first1 = D. | title = Practical advice regarding problematic pigmented lesions. | journal = J Am Acad Dermatol | volume = 67 | issue = 1 | pages = 148-55 | month = Jul | year = 2012 | doi = 10.1016/j.jaad.2012.04.006 | PMID = 22703907 }}</ref>
{{Main|Dysplastic nevus}}


Epidemiology:
==Desmoplastic melanocytic nevus==
*Children & adolescents.
*[[AKA]] ''sclerosing melanocytic nevus''.


Treatment:
===General===
*Complete excision.<ref name=pmid12140468>{{Cite journal  | last1 = Gelbard | first1 = SN. | last2 = Tripp | first2 = JM. | last3 = Marghoob | first3 = AA. | last4 = Kopf | first4 = AW. | last5 = Koenig | first5 = KL. | last6 = Kim | first6 = JY. | last7 = Bart | first7 = RS. | title = Management of Spitz nevi: a survey of dermatologists in the United States. | journal = J Am Acad Dermatol | volume = 47 | issue = 2 | pages = 224-30 | month = Aug | year = 2002 | doi =  | PMID = 12140468 }}</ref>
*Benign.


===Gross===
===Gross===
*Usually face ''or'' extremity.<ref name=Ref_Derm449>{{Ref Derm|449}}</ref>
*Usu. "small" and symmetric.
 
Clinical DDx:
*[[Dermatofibroma]].
*[[Dermal scar]].


===Microscopic===
===Microscopic===
Features:<ref name=Ref_WMSP499>{{Ref WMSP|499}}</ref>
Features:<ref name=Ref_Derm_464>{{Ref Derm|464}}</ref>
*Architecture:
*[[Compound nevus]] ''or'' [[intradermal nevus]] with prominent dermal fibrosis.
**Nests of cells (spindle, epithelioid or spindle/epithelioid) - in both dermis and epidermis.
**Fibrosis: extra pink - versus surrounding.
***Nests are vertically arranged, i.e. the long axis of the nests are perpendicular to the skin surface.
****Nest arrangement/orientation described as "cluster of bananas".
*+/-Hyperkeratosis (more keratin, i.e. thick stratum corneum).
*+/-Hypergranulosis (thick stratum granulosum).
*+/-Acanthosis (thick stratum spinosum).
*Kamino bodies (also written ''Camino bodies'') - dense eosinophilic bodies.<ref name=PMC2797485>{{Cite journal  | last1 = Kirkwood | first1 = John M. | last2 = Jukic | first2 = Drazen | last3 = Averbook | first3 = Bruce J. | last4 = Sender | first4 = Leonard S. | title = Melanoma in Pediatric, Adolescent, and Young Adult Patients | journal = Semin Oncol. | volume = 36 | issue = 5 | pages = 419-31 | month = October | year = 2009 | doi =  | PMID =  | URL = http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2797485/?tool=pmcentrez |PMC = 2797485 }}</ref>
**Apoptotic cells.
**Kamino bodies are rare in melanoma.


Notes:
DDx:
*'''Never''' in the setting of solar elastosis.<ref>Jakubovic, H. 16 July 2010.</ref>
*[[Desmoplastic neurotropic malignant melanoma]] - usually mitotic figures, nuclear atypia (enlarged, hyperchromatic).
**If there is solar elastosis -- it's melanoma.
*[[Dermatofibroma]].
*[[Dermal scar]] - no adnexal structures.


DDx:
===IHC===
*[[Malignant melanoma]].
Features:<ref name=Ref_Derm_464>{{Ref Derm|464}}</ref>
*[[Pigmented spindle cell nevus of Reed]].
*Melan A (MART-1) +ve.
**Usually -ve in desmoplastic melanoma.<ref name=Ref_Derm_464>{{Ref Derm|464}}</ref>
*S-100 +ve.
**Should stain approximally the same number of cells as Melan A.
*Ki-67 -- only rare cells.


Images:
==Nodal nevus==
*www:
*AKA ''nevus in lymph node'' and ''benign nevus cells in lymph node''.
**[http://www.drmihm.com/cases/case.cfm?CaseID=51 Spitz nevus - collection of images (drmihm.com)].
{{Main|Nodal nevus}}
**[http://alf3.urz.unibas.ch/pathopic/e/getpic-fra.cfm?id=006734 Spitz nevus with arrow to camino body (unibas.ch)].
*[[WC]]:
**[http://commons.wikimedia.org/wiki/File:Spitz_nevus_-_intermed_mag.jpg Spitz nevus - intermed. mag. (WC)].


=Miscellaneous=
==Blue nevus==
==Blue nevus==
:'''''Common blue nevus''' redirects here''.
*Abbreviated ''BN''.
*Abbreviated ''BN''.
===General===
===General===
*Usually head & neck, extremities (e.g. dorsum of wrist or foot) or buttock.<ref name=Ref_Derm456>{{Ref Derm|456}}</ref>
*Usually head & neck, extremities (e.g. dorsum of wrist or foot) or buttock.<ref name=Ref_Derm456>{{Ref Derm|456}}</ref>
*Clinically confused with [[malignant melanoma]].<ref name=Ref_PCPBoD8_592>{{Ref PCPBoD8|592}}</ref>
*Clinically confused with [[malignant melanoma]].<ref name=Ref_PCPBoD8_592>{{Ref PCPBoD8|592}}</ref>
*Second most common melanocytic lesion of the oral cavity.<ref>URL: [http://emedicine.medscape.com/article/1079272-overview http://emedicine.medscape.com/article/1079272-overview]. Accessed on: 10 December 2012.</ref>
**Most common melanocytic lesion ''[[intramucosal melanocytic nevus]]''.


Clinical:
===Gross===
*Blue flat or slightly raised lesion.
*Blue flat or slightly raised lesion.


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Notes:<ref name=Ref_Derm457>{{Ref Derm|457}}</ref>
Notes:<ref name=Ref_Derm457>{{Ref Derm|457}}</ref>
*No epidermal component.
*Classically no epidermal component.
** The entity ''compound blue nevus'' has been described; it is rare.<ref name=pmid2221938>{{Cite journal  | last1 = Kamino | first1 = H. | last2 = Tam | first2 = ST. | title = Compound blue nevus: a variant of blue nevus with an additional junctional dendritic component. A clinical, histopathologic, and immunohistochemical study of six cases. | journal = Arch Dermatol | volume = 126 | issue = 10 | pages = 1330-3 | month = Oct | year = 1990 | doi =  | PMID = 2221938 }}
</ref>
*May be assoc. with a hair follicle.
*May be assoc. with a hair follicle.


DDx:
DDx:
*[[Malignant melanoma]] - often lacks a Grenz zone (lesion in papillary dermis),<ref name=pmid16446716/> mitotic figures, [[necrosis]], cytologic atypia, asymmetry (architecture, pigment).
*Atypical blue nevus - have some of the features of melanoma.
*[[Clear cell sarcoma]].
*[[Dermatofibroma]] - esp. amelanotic BN.
*[[Dermatofibroma]] - esp. amelanotic BN.
*[[Malignant melanoma]].
*[[Combined melanocytic nevus]] - blue nevus found together with another nevus (classically [[common melanocytic nevus]]), superficial.
*[[Clear cell sarcoma]].
*[[Pigmented epithelioid melanocytoma]] - superificial dermis, has nuclear atypia.
*[[Vascular lesions]] ([[venous lake]], [[hemangioma]]).


Images:
====Images====
*[http://commons.wikimedia.org/wiki/File:Blue_nevus_%281_of_4%29.jpg Blue nevus (WC)].
<gallery>
*[http://commons.wikimedia.org/wiki/File:Blue_nevus_-_very_low_mag.jpg Blue nevus - very low mag. (WC)].  
Image:Blue_nevus_%281_of_4%29.jpg | Blue nevus (WC)
*[http://commons.wikimedia.org/wiki/File:Blue_nevus_-_intermed_mag.jpg Blue nevus - intermed. mag. (WC)].
Image:Blue_nevus_-_very_low_mag.jpg | Blue nevus - very low mag. (WC)
Image:Blue_nevus_-_intermed_mag.jpg | Blue nevus - intermed. mag. (WC)
</gallery>
www:
*[http://www.dermatopathonline.com/blue%20nevus2.html Several types of blue nevi (dermatopathonline.com)].
*[http://www.nature.com/modpathol/journal/v19/n2s/fig_tab/3800516f25.html#figure-title Melanoma that looks a bit like a blue nevus (nature.com)].<ref name=pmid16446716>{{Cite journal  | last1 = Magro | first1 = CM. | last2 = Crowson | first2 = AN. | last3 = Mihm | first3 = MC. | title = Unusual variants of malignant melanoma. | journal = Mod Pathol | volume = 19 Suppl 2 | issue =  | pages = S41-70 | month = Feb | year = 2006 | doi = 10.1038/modpathol.3800516 | PMID = 16446716 }}</ref>


====Variants of blue nevus====
====Variants of blue nevus====
Several histologic variants:<ref name=Ref_Derm457>{{Ref Derm|457}}</ref>
Several histologic variants:<ref name=Ref_Derm457>{{Ref Derm|457}}</ref>
*Common blue nevus - the BN not otherwise specified.
*Common blue nevus - the blue nevus not otherwise specified.
*[[Cellular blue nevus]].
*Amelanotic blue nevus - may be confused with a [[dermatofibroma]].
*Sclerosing blue nevus - has stromal fibrosis.
*Sclerosing blue nevus - has stromal fibrosis.
*Amelanotic blue nevus - may be confused with a [[dermatofibroma]].
*Epithelioid blue nevus.
*Epithelioid blue nevus.
*Cellular blue nevus.
 
Memory device:
*''C CASE'' = '''C'''ommon, '''C'''ellular, '''A'''melanotic, '''S'''clerosing, '''E'''pithelioid.
 
===IHC===
*HMB-45 diffusely +ve.{{fact}}
**Melanoma patchy +ve.
*MART-1 diffusely +ve.
*Ki-67 low.


===Sign out===
===Sign out===
<pre>
<pre>
SKIN LESION, RIGHT WRIST DORSUM, PUNCH BIOPSY:  
SKIN LESION, RIGHT WRIST DORSUM, PUNCH BIOPSY:  
- COMMON BLUE NEVUS.
- COMMON BLUE NEVUS.
</pre>
 
<pre>
SKIN LESION, LEFT SHIN, PUNCH BIOPSY:
- SCLEROSING BLUE NEVUS.
</pre>
</pre>
====Micro====
The sections show pigmented spindle cells in the dermis between collagen bundles. The spindle cells show no nuclear atypia and no mitotic activity is appreciated.
The lesion does not extend into the epidermis and is separated from it by a Grenz zone. There are no melanocyte nests. There is no significant inflammation. The lesion is completely excised.
The pigmented cells are negative on the Prussian blue stain.
=====Sclerosing blue nevus=====
The sections show pigmented spindle cells in the dermis between densely packed collagen fibres. The spindle cells show no significant nuclear atypia, and no mitotic activity is appreciated.  The lesion extends up to the epidermis; however, it does not appear to involve the epidermis. The overlying epidermis has hyperkeratosis; otherwise, it is unremarkable. There are no nests of melanocytes. There is no significant inflammation. The lesion is completely excised in the plane of section.


==Cellular blue nevus==
==Cellular blue nevus==
===General===
===General===
*Congenital or acquired.
*Congenital or acquired.
*Usu. scalp or butt.
*Usually scalp or butt.
*Variant of the ''[[common blue nevus]]''.


===Microscopic===
===Microscopic===
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*[http://www.dermpedia.org/case/cellular-blue-nevus-0 Cellular blue nevus (dermpedia.org)].
*[http://www.dermpedia.org/case/cellular-blue-nevus-0 Cellular blue nevus (dermpedia.org)].


==Acral nevus==
==Combined melanocytic nevus==
*[[AKA]] melanocytic nevus with intraepidermal ascent of cells (MANIAC).
*[[AKA]] ''combined nevus''.
===General===
===General===
*Palms or soles.
*Uncommon.
*Morphologic features of two types of melanocytic nevi.
**Most common: [[blue nevus]] and common nevus.<ref name=pmid21881487>{{Cite journal  | last1 = Baran | first1 = JL. | last2 = Duncan | first2 = LM. | title = Combined melanocytic nevi: histologic variants and melanoma mimics. | journal = Am J Surg Pathol | volume = 35 | issue = 10 | pages = 1540-8 | month = Oct | year = 2011 | doi = 10.1097/PAS.0b013e31822e9f5e | PMID = 21881487 }}</ref>


===Microscopic===
===Microscopic===
Features:
Features:<ref name=pmid21881487/>
*Nevus with intraepidermal ascent of cells.
*Morphologic features of two types of melanocytic nevi.
 
Notes:
*Intraepidermal ascent of cells is usually suggestive of melanoma.
**In acral sites the criteria are relaxed, i.e. this is considered benign for this site.
 
==Clark nevus==
*[[AKA]] ''dysplastic nevus''.
*[[AKA]] ''dysplastic melanocytic nevus''.
 
===General===
*Benign.
*Clark nevi are considered a risk factor for [[malignant melanoma|melanoma]] and may be a precursor of melanoma, as the name ''dysplastic nevus'' suggests.<ref name=pmid21308311>{{Cite journal  | last1 = Rezze | first1 = GG. | last2 = Leon | first2 = A. | last3 = Duprat | first3 = J. | title = Dysplastic nevus (atypical nevus). | journal = An Bras Dermatol | volume = 85 | issue = 6 | pages = 863-71 | month = Dec | year = 2010 | doi =  | PMID = 21308311 }}</ref>  
**Most melanoma cases do not have evidence of a pre-existing (dysplastic) nevus.<ref name=pmid21715047>{{Cite journal  | last1 = Longo | first1 = C. | last2 = Rito | first2 = C. | last3 = Beretti | first3 = F. | last4 = Cesinaro | first4 = AM. | last5 = Piñeiro-Maceira | first5 = J. | last6 = Seidenari | first6 = S. | last7 = Pellacani | first7 = G. | title = De novo melanoma and melanoma arising from pre-existing nevus: in vivo morphologic differences as evaluated by confocal microscopy. | journal = J Am Acad Dermatol | volume = 65 | issue = 3 | pages = 604-14 | month = Sep | year = 2011 | doi = 10.1016/j.jaad.2010.10.035 | PMID = 21715047 }}</ref>
*Large numbers of these nevi (10-100) are seen in ''dysplastic nevus syndrome''.<ref name=omim155600>{{OMIM|155600}}</ref>
**Individuals with this syndrome have an increased risk of melanoma and approximately one third of their melanomas arise from a ''Clark nevus''. The other two thirds arise ''de novo''.
 
Clinical:<ref name=pmid22220461>{{Cite journal  | last1 = Dediol | first1 = I. | last2 = Bulat | first2 = V. | last3 = Zivković | first3 = MV. | last4 = Marković | first4 = BM. | last5 = Situm | first5 = M. | title = Dysplastic nevus--risk factor or disguise for melanoma. | journal = Coll Antropol | volume = 35 Suppl 2 | issue =  | pages = 311-3 | month = Sep | year = 2011 | doi =  | PMID = 22220461 }}</ref>
*Associated with sun exposure.
 
Treatment:
*Clark nevi with severe nuclear atypia are treated like melanoma.
 
===Gross===
Features:<ref name=pmid22220461/>
*"Ugly duckling sign" - lesion looks different than the rest.
*ABCDE criteria of in melanoma.
 
===Microscopic===
Features:<ref name=Ref_WMSP502>{{Ref WMSP|502}}</ref>
*Melanocytes "bridges" between sides of rete ridges.
*Drapping fibrous tissue - "lamellar fibrosis" - collagen deep to epidermis.
*Usually moderate nuclear atypia (small nucleoli present) - see ''grading'' section.
*Junctional component (cells in the epidermis at the DE junction) larger than the intradermal component - ''shoulder phenomenon''.


DDx:
DDx:
*[[Malignant melanoma]].
*[[Malignant melanoma]].
*[[Compound melanocytic nevus]].
*[[Pigmented epithelioid melanocytoma]] - superificial dermis, has nuclear atypia.
 
Images:
*[http://commons.wikimedia.org/wiki/File:Dysplastic_nevus_-_low_mag.jpg Dysplastic nevus - low mag. (WC)].
*[http://commons.wikimedia.org/wiki/File:Dysplastic_nevus_-_intermed_mag.jpg Dysplastic nevus - intermed. mag. (WC)].
*[http://commons.wikimedia.org/wiki/File:Dysplastic_nevus_-_add_-_high_mag.jpg Dysplastic nevus - high mag. (WC)] - shows bridging and lamellar fibrosis.
*[http://commons.wikimedia.org/wiki/File:Dysplastic_nevus_-_add_-_very_high_mag.jpg Dysplastic nevus - very high mag. (WC)] - shows bridging and lamellar fibrosis.
 
====Grading====
These lesions are usually graded:<ref name=Ref_Derm447-8>{{Ref Derm|447-8}}</ref>
{| class="wikitable sortable"
! Grade
! Size of nucleus
! Other features
|-
| Mild
| 1x keratinocyte nucleus
| no [[nucleoli]]/very small nucleoli †,<ref name=pmid12920220>{{Cite journal  | last1 = Arumi-Uria | first1 = M. | last2 = McNutt | first2 = NS. | last3 = Finnerty | first3 = B. | title = Grading of atypia in nevi: correlation with melanoma risk. | journal = Mod Pathol | volume = 16 | issue = 8 | pages = 764-71 | month = Aug | year = 2003 | doi = 10.1097/01.MP.0000082394.91761.E5 | PMID = 12920220 | URL = http://www.nature.com/modpathol/journal/v16/n8/full/3880837a.html }}</ref> slight hyperchromasia
|-
| Moderate
| 1-2x keratinocyte nucleus
| small nucleoli †, irregular nuclear contours
|-
| Severe
| >2x keratinocyte nucleus
| prominent nucleoli †‡
|}
† The sizes "very small", "small" and "prominent" are not defined; it is suggested that "very small" is visible with the 40x objective, "small" with the 20x objective and "prominent" with the 10x objective.  Focal, rare small nucleoli are not significant; they can be seen in benign melanocytic nevi.<br>
‡ Prominent nucleoli (alone) is considered enough to call "severe".<ref name=Ref_Derm447-8>{{Ref Derm|447-8}}</ref>


===Sign out===
===Sign out===
<pre>
<pre>
SKIN, EXCISION:
A. SKIN LESION, LEFT UPPER ARM, PUNCH BIOPSY:
- DYSPLASTIC NEVUS WITH MILD NUCLEAR ATYPIA.
- BENIGN COMBINED MELANOCYTIC NEVUS (INTRADERMAL MELANOCYTIC NEVUS AND BLUE NEVUS).
- MARGINS NEGATIVE FOR NEVUS CELLS.
</pre>
</pre>


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{{Main|Neurocristic hamartoma}}
{{Main|Neurocristic hamartoma}}


==See also==
=See also=
*[[Dermatopathology]].
*[[Dermatopathology]].
*[[Cytopathology]].
*[[Cytopathology]].
*[[Non-malignant skin disease]].
*[[Non-malignant skin disease]].
*[[Pigmented lesions of the oral cavity]].
*[[Melanosis coli]].
*[[Small bowel pseudomelanosis]].


==References==
=References=
{{reflist|2}}
{{reflist|2}}
=External links=
*[http://www.youtube.com/watch?v=_4jgUcxMezM Dear 16 year-old me (youtube.com)] - with Dr. G.


[[Category:Dermatopathology]]
[[Category:Dermatopathology]]
[[Category:Melanocytic lesions]]
Michael
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