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[[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]]).
'''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]]).


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=Lentiginous melanocytic lesions=
=Lentiginous melanocytic lesions=
==Lentigo simplex==
==Lentigo simplex==
*[[AKA]] ''simple lentigo''.<ref>URL: [http://www.dermnetnz.org/lesions/lentigo-simplex.html http://www.dermnetnz.org/lesions/lentigo-simplex.html]. Accessed on: 27 March 2013.</ref>
{{Main|Lentigo simplex}}
===General===
*Benign.
*Usually <40 years old.
 
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]].
 
Associated syndromes:<ref name=dermamin_ls>URL: [http://dermaamin.com/site/histopathology-of-the-skin/64-l/1852-lentigo-simplex-.html http://dermaamin.com/site/histopathology-of-the-skin/64-l/1852-lentigo-simplex-.html]. Accessed on: 17 December 2012.</ref>
*[[Peutz-Jeghers syndrome]].
*[[LEOPARD syndrome]].
*[[LAMB syndrome]].
 
===Gross===
*Small flat pigmented lesion.<ref name=Ref_WMSP498>{{Ref WMSP|498}}</ref>
 
DDx - clinical:
*[[Melanocytic nevus]].<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>
 
===Microscopic===
Features:<ref name=Ref_WMSP498>{{Ref WMSP|498}}</ref>
*Melanocytes in epidermis only.
**Melanocytes basally located (normal location) with hyperpigmentation.
*No melanocytic nests.
*+/-Mild/moderate elongation of the rete ridges.<ref name=pmid19536147/>
 
DDx:<ref name=humpath_ls/>
*[[Solar lentigo]] - solar elastosis, usu. in sun exposed areas.
*[[Ephelis]] (freckle) - change with UV light exposure.
*Melanotic macule.
*[[Lentiginous nevus]] - has melanocytic nests.
 
====Images====
*[http://dermaamin.com/site/histopathology-of-the-skin/64-l/1852-lentigo-simplex-.html Lentigo simplex - several images (dermamin.com)].<ref name=dermamin_ls/>
*[http://www.humpath.com/IMG/jpg/lentigo_simplex_20x.jpg Lentigo simplex (humpath.com)].<ref name=humpath_ls>URL: [http://www.humpath.com/?lentigo-simplex http://www.humpath.com/?lentigo-simplex]. Accessed on: 17 December 2012.</ref>
<gallery>
Image:Skin_Tumors-171.jpg | Simple lentigo. (WC)
</gallery>
 
===Sign out===
<pre>
SKIN LESION, LEFT ABDOMEN, BIOPSY:
- SIMPLE LENTIGO, COMPLETELY EXCISED IN THE PLANE OF SECTION.
</pre>
 
<pre>
SKIN LESION, LEFT ABDOMEN, BIOPSY:
- BENIGN SIMPLE LENTIGO.
</pre>
 
====Micro====
The sections show skin with increased numbers of small pigmented melanocytes at the dermal-epidermal junction. The rete ridges are mildly elongated. No solar damage is apparent. No dermal melanocytes are identified. No melanocytic nests are identified. No nuclear atypia is apparent.


==Solar lentigo==
==Solar lentigo==
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**Classically at the tips of the rete ridges.
**Classically at the tips of the rete ridges.
*No (melanocyte) nuclear atypia.
*No (melanocyte) nuclear atypia.
*Solar damage ([[solar elastosis]]).<ref name=pmid19536147/>
*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:
Notes:
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*[[Lichen planus-like keratosis]].
*[[Lichen planus-like keratosis]].
*Pigmented [[seborrheic keratosis]].
*Pigmented [[seborrheic keratosis]].
*[[Ephelis]] (freckle).


Images:
====Images====
*[http://commons.wikimedia.org/wiki/File:Skin_tumors_181.jpg Solar lentigo (WC)].
<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>
*[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>


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*[[AKA]] ''intradermal melanocytic nevus''.
*[[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>
*[[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}}
*Only in the dermis - '''key feature'''.
*+/-Adipocytes - uncommon.<ref name=pmid9810886>{{Cite journal  | last1 = Eng | first1 = W. | last2 = Cohen | first2 = PR. | title = Nevus with fat: clinical characteristics of 100 nevi containing mature adipose cells. | journal = J Am Acad Dermatol | volume = 39 | issue = 5 Pt 1 | pages = 704-11 | month = Nov | year = 1998 | doi =  | PMID = 9810886 }}</ref>
 
Note:
*In the oral cavity these are known as ''[[intramucosal melanocytic nevus|intramucosal nevi]]''.


===Sign out===
===Sign out===
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====Compound melanocytic nevus====
====Compound melanocytic nevus====
<pre>
{{Main|Compound nevus}}
SKIN LESION, RIGHT NECK, SHAVE BIOPSY:
- BENIGN COMPOUND NEVUS.
</pre>
 
=====Micro=====
The sections show melanocytes in the dermis and epidermis. The lesion is symmetrical in its architecture and pigment distribution. There is no pagetoid spread of melanocytes in the epidermis. Superficially, melanocytes are in nests. Melanocytes show no apparent cytologic atypia and mature with depth. No mitotic activity is appreciated.
 
The lesion is completely excised in the plane of section.
 
======Barely compound======
The sections show melanocytes predominantly in the dermis. Rare melanocytic nests are seen at the dermal-epidermal junction. There is no pagetoid spread of melanocytes in the epidermis. The lesion is symmetrical in its architecture. Superficially, melanocytes are in nests and pigment is present.  The melanocytes mature with depth. No mitotic activity is appreciated.
 
The lesion is present at the margin.
 
======CN with congenital features======
The sections show melanocytes in the dermis and epidermis. There is no pagetoid spread of melanocytes in the epidermis. Superficially, melanocytes are in nests. Melanocytes show mild nuclear enlargement but mature with depth. Nucleoli are not prominent. Melanocytes are found adjacent to adnexal structures and blood vessels. No mitotic activity is appreciated. The lesion is incompletely excised.


====Intradermal melanocytic nevus====
====Intradermal melanocytic nevus====
<pre>
{{Main|Intradermal nevus}}
SKIN LESION, BACK, PUNCH BIOPSY:
- BENIGN INTRADERMAL NEVUS.
</pre>
 
=====Adipocytes present=====
<pre>
SKIN LESION, BACK, PUNCH BIOPSY:
- BENIGN INTRADERMAL NEVUS WITH MATURE ADIPOCYTES.
</pre>
 
=====Clinically suspicious=====
<pre>
SKIN LESION, LEFT UPPER ARM, PUNCH BIOPSY:
- BENIGN INTRADERMAL NEVUS, INCOMPLETELY EXCISED.
 
COMMENT:
HMB-45 marks very rare superficial cells. Ki-67 staining does not show apparent melanocyte
staining. MITF marks the melanocytes and demonstrates maturation of the melanocytes with depth.
</pre>
 
=====Micro=====
The sections show melanocytes in the dermis separated from the epidermis by a Grenz zone.  The lesion is symmetrical in its architecture and pigment distribution.  Superficially, melanocytes are in nests.  Melanocytes mature with depth. No mitotic activity is appreciated.
 
The lesion is completely excised in the plane of section.


==Congenital-pattern nevus==
==Congenital-pattern nevus==
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==Pigmented spindle cell nevus==
==Pigmented spindle cell nevus==
*[[AKA]] ''pigmented spindle cell nevus of Reed''.
*[[AKA]] ''pigmented spindle cell nevus of Reed''.
 
{{Main|Pigmented spindle cell nevus}}
===General===
*Uncommon.
*Women in teens & 20s.
*Location: shoulder, pelvic girdle region.
 
===Microscopic===
Features:<ref name=Ref_WMSP500>{{Ref WMSP|500}}</ref>
*Nests of heavily pigmented spindle cells at dermal-epidermal junction - '''key feature'''.
**Nevoid cells in epidermis & dermis - form "basket weave" pattern
*Well-circumscribed lesion.
 
Notes:
*No epithelioid nevus cells.
 
DDx:
*[[Spitz nevus]].
*[[Malignant melanoma]].
 
====Images====
<gallery>
Image:Pigmented_spindle_cell_nevus_-_low_mag.jpg | PSCN - low mag. (WC)
Image:Pigmented_spindle_cell_nevus_-_2_-_intermed_mag.jpg | PSCN - intermed. mag. (WC)
Image:Pigmented_spindle_cell_nevus_-_2_-_high_mag.jpg | PSCN - high mag. (WC)
</gallery>
www:
*[http://www.histopathology-india.net/Reed.htm Reed nevus - collection (histopathology-india.net)].
 
===Sign out===
<pre>
SKIN LESION, RIGHT POSTERIOR NECK, EXCISION:
- PIGMENTED SPINDLE CELL NEVUS OF REED.
-- COMPLETELY EXCISED (CLEARANCE ~ 1 MM).
</pre>
 
====Micro====
The sections show spindled pigmented melanocytes in nests 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. Melanophages are present in the superficial
dermis. The lesion is completely excised in the plane of section.


==Spitz nevus==
==Spitz nevus==
*[[AKA]] ''epithelioid and spindle-cell nevus''.
*[[AKA]] ''epithelioid and spindle cell nevus''.
 
{{Main|Spitz nevus}}
===General===
*May be very difficult to differentiate from [[melanoma]].
 
Epidemiology:
*Children & adolescents.
 
Treatment:
*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>
 
===Gross===
*Usually face ''or'' extremity.<ref name=Ref_Derm449>{{Ref Derm|449}}</ref>
 
===Microscopic===
Features:<ref name=Ref_WMSP499>{{Ref WMSP|499}}</ref>
*Architecture:
**Nests of cells (spindle, epithelioid or spindle/epithelioid) - in both dermis and epidermis.
***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:
*'''Never''' in the setting of [[solar elastosis]].<ref>Jakubovic, H. 16 July 2010.</ref>
**If there is solar elastosis -- it's melanoma.
 
DDx:
*[[Malignant melanoma]] - so-called ''Spitzoid melanoma''.
*[[Pigmented spindle cell nevus of Reed]].
 
====Images====
<gallery>
Image:Spitz_nevus_-_low_mag.jpg | Spitz nevus - low mag. (WC)
Image:Spitz_nevus_-_intermed_mag.jpg | Spitz nevus - intermed. mag. (WC)
Image:Spitz_nevus_-_high_mag.jpg | Spitz nevus - high mag. (WC)
</gallery>
www:
*[http://www.drmihm.com/cases/case.cfm?CaseID=51 Spitz nevus - collection of images (drmihm.com)].
*[http://alf3.urz.unibas.ch/pathopic/e/getpic-fra.cfm?id=006734 Spitz nevus with arrow to camino body (unibas.ch)].
 
===IHC===
*HMB-45 -ve at deep aspect.
*Ki-67 low.


==Acral nevus==
==Acral nevus==
*[[AKA]] ''melanocytic nevus with intraepidermal ascent of cells'' (MANIAC).
*[[AKA]] ''melanocytic nevus with intraepidermal ascent of cells'' ([[MANIAC]]).
*[[AKA]] ''volar nevus''.
*[[AKA]] ''volar nevus''.
===General===
{{Main|Acral nevus}}
*Palms ''or'' soles.
 
Note:
*''Volar'' refers to the palmar aspect ''or'' plantar aspect.<ref>URL: [http://www.medterms.com/script/main/art.asp?articlekey=9907 http://www.medterms.com/script/main/art.asp?articlekey=9907]. Accessed on: 14 January 2013.</ref>
 
===Gross===
*Pigmented lesion.
 
Note:
*Should be bisected perpendicular to the dermatoglyphs (ridges).<ref name=pmid22703907/>
**Lesions sectioned parallel to the ridges (on microscopy) may appear to have confluent junctional nests (leading to the diagnosis of melanoma).
===Microscopic===
Features:
*Acral skin:
**Thick stratum corneum (hyperkeratotic).
**Thick stratum spinosum (acanthotic).
*Nevus with intraepidermal ascent of cells.
**May be referred to as ''Pagetoid scatter''.
**Should '''not''' be present at the edge of the lesion - '''key feature'''.<ref name=pmid22703907/>
 
Notes:
*Intraepidermal ascent of cells is usually suggestive of melanoma.
**In acral sites (esp. at the centre of a lesion) the criteria are relaxed, i.e. this is considered benign for this site.
*Nests in the ridges raise the suspicion of melanoma.
**Memory device "ridges are risky, furrows are fine".<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>
 
DDx:
*Acral lentiginous [[melanoma]].


==Dysplastic melanocytic nevus==
==Dysplastic melanocytic nevus==
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**Should stain approximally the same number of cells as Melan A.
**Should stain approximally the same number of cells as Melan A.
*Ki-67 -- only rare cells.
*Ki-67 -- only rare cells.
==Nodal nevus==
*AKA ''nevus in lymph node'' and ''benign nevus cells in lymph node''.
{{Main|Nodal nevus}}


=Miscellaneous=
=Miscellaneous=
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DDx:
DDx:
*[[Malignant melanoma]] - mitotic figures, necrosis, cytologic atypia, asymmetry (architecure, pigment).
*[[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.
*Atypical blue nevus - have some of the features of melanoma.
*[[Clear cell sarcoma]].
*[[Clear cell sarcoma]].
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www:
www:
*[http://www.dermatopathonline.com/blue%20nevus2.html Several types of blue nevi (dermatopathonline.com)].
*[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====
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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 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. There are no melanocyte nests. There is no significant inflammation. The lesion is completely excised.
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.
The pigmented cells are negative on the Prussian blue stain.
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*[[Cytopathology]].
*[[Cytopathology]].
*[[Non-malignant skin disease]].
*[[Non-malignant skin disease]].
*[[Pigmented lesions of the oral cavity]].
*[[Melanosis coli]].
*[[Small bowel pseudomelanosis]].


=References=
=References=
Michael
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