Junctional nevus

Author: Mikael Häggström

Junctional nevus (here seen in H&E stain and Melan A stain), where all nests are continuous with the epidermis.

Comprehensiveness

On this resource, the following formatting is used for comprehensiveness:

• Minimal depth
• (Moderate depth)
• ((Comprehensive))

A suspected dysplastic nevus (also called dysplastic melanocytic nevus) generally presents as a dark skin focality.

Fixation

Generally 10% neutral buffered formalin.

Gross processing of skin excisions

Gross pathologic processing of skin excisions

	Lesion size
	<4 mm	4 - 8 mm	9 - 15 mm
Benign appearance
Suspected malignancy

In table above, each top image shows recommended lines for cutting out slices to be submitted for further processing. Bottom image shows which side of the slice that should be put to microtomy. Dashed lines here mean that either side could be used. Further information: Gross processing of skin excisions

Microscopic evaluation

A junctional nevus is characterized by:

• Rounded melanocyte nests on the epidermal side of dermoepidermal junction
• Variable lentiginous melanocytic hyperplasia

Differential diagnosis

• 

  Melanoma in situ, by higher atypia and dysplasia (see table in the grading section).

• 

  Dermal nevus, with nevus cells enclosed within the dermis.

• Compound nevus, with nevus cells in both dermis and epidermis.

• Epidermal nevus, nests of nevus cells enclosed within the epidermis.

Grading

((Grade a nevus into either low or high grade by the following algorithm:))

In uncertain cases, more specific grading, and/or differentiation from a non-atypical congenital nevus and suspected melanoma, the following table can be used to determine the most fitting diagnosis:

Comparison of congenital pattern nevus, dysplastic nevus and suspected melanoma  

Parameter		Non-atypical congenital pattern	Low-grade dysplastic nevus		High-grade dysplastic nevus	Suspected melanoma in situ
			Mild dysplasia	Moderate dysplasia	Severe dysplasia
Macroscopic	Lateral circumscription	Sharp	Slightly diminished	Moderate		Poor
	Symmetry	Good			Often broken	Rare
Structural (Low mag.)	Delimitation		Rarely diffuse	Sometimes diffuse	Often diffuse
	Lentiginous proliferation		Yes, along with rete pegs	Yes, along with and focally between rete pegs	Yes, along with and focally between rete pegs	Yes partially continuous, multilayered
	Bridging		Rarely	Often
	Confluent nests		Rarely	Sometimes	Often	Often widespread
	Pigment distribution		Regular	Irregular
	Suprabasal presence (less than most superficial third of subcorneal epidermis)	Occasionally centrally	No or rarely	Occasionally centrally		Yes, multifocal
	Pagetoid migration including superficial third of subcorneal epidermis		No	No	Yes, in a maximum of 2 HPF centrally, but not peripherally	Yes, multifocal and/or in periphery Peripheral.
	Extended rete pegs	Ocassional	Yes, regular	Yes, varying	Yes, often irregular	Varying, flattened
	Concentric fibrosis	Regressive	Yes			Occasional
	Lamellar fibrosis		Rarely	Often	Often pronounced	Occasional
	Lymphocytic infiltrate		Mild, perivascular	Mild or moderate, perivascular	Varying	Varying
	Suprapapillary plate involvement	No		Usually no	Often	Yes
Cellular (high mag.)	Image
	Junctional extension	Unusual	Usual			Extensive
	Nuclear size	Age-related	Small	Medium	Large	Medium or large. Pleomorphic
	Nuclear pleomorphism		Slight	Prominent
	Chromatin pattern	Uniform	Condensed	Partically expanded	Expanded, coarse in some cells	Expanded, hyperchromatic, coarse. Usually granular.
	Nucleoli	Age-related	Small	Medium	Large	Usually large
	Mitoses	Few superficial				Superficial and deep
	Histological regression		Usually		Usually not
	Percentage of atypical melanocytes		<10%	About 10 - 50%	about 50-90%	Usually> 90%
	Intradermal melanocytic atypia		No	Rarely, in superficial part	Can be detected in superficial part
	Intradermal melanocyte maturation		Yes	Yes, can be partial	Yes, can be partial	Variable

In suspected but not certain nevus or melanoma in situ, generally perform immunohistochemistry with SOX10, whereby melanocyte proliferation and nuclear pleomorphism is easier to see.

• 

  SOX10 immunohistochemistry of a junctional nevus, with atypical melanocytic proliferation, seen mainly in hair follicles.

• 

  SOX10 immunohistochemistry of lentigo maligna, showing an increased number of melanocytes along stratum basale, and nuclear pleumorphism.

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In contrast, normal skin (pictured) has a melanocyte about every 4 cells along the basement membrane.

Report

• Size
• Preferably findings included in table.
• ((Most likely grade if possible.))

  See also: General notes on reporting

Main page

• Main page of Patholines