Dermal nevus

Author: Mikael Häggström
A suspected dermal (or intradermal nevus) generally presents as a dark skin focality.

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

Comprehensiveness

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

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

Microscopic evaluation

• Irregularly distributed dermal nests of melanocytes.
• Atypia

• 

  Dermal nevus

• 

  A dermal nevus infrequently shows multinucleated giant cells as shown.

Subtyping

Blue nevus: Where the pigment is deeper in the skin than in ordinary nevi.

Differential diagnosis

Mainly:

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

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

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  Invasive melanoma of the skin, has more atypia and dysplasia (see table in the grading section).

Grading

(Grade a dermal 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 invasive melanoma, the following table can be used to determine the most fitting diagnosis:

Comparison of dermal nevus and suspected invasive melanoma  

Parameter		Non-dysplastic dermal nevus	Low-grade dysplastic dermal nevus		High-grade dysplastic dermal nevus	Suspected invasive melanoma
			Mild dysplasia	Moderate dysplasia	Severe dysplasia
Macroscopic	Lateral circumscription	Sharp	Slightly diminished	Moderate		Poor
	Symmetry	Good			Often broken	Rare
Structural (Low mag.)	Micrograph
	Delimitation		Rarely diffuse	Sometimes diffuse	Often diffuse
	Confluent nests		Rarely	Sometimes	Often	Often widespread
	Pigment distribution	Regular		Irregular
	Concentric fibrosis	Regressive (see below table)	Yes			Occasional
	Lamellar fibrosis		Rarely	Often	Often pronounced	Occasional
	Lymphocytic infiltrate		Mild, perivascular	Mild or moderate, perivascular	Varying	Varying
Cellular (high mag.)	Micrographs
	Nuclear size		Small	Medium	Large	Medium or large. Pleomorphic
	Nuclear pleomorphism	Slight superficial	Slight	Prominent
	Chromatin pattern	Uniform	Condensed	Partically expanded	Expanded, coarse in some cells	Expanded, hyperchromatic, coarse. Usually granular.
	Nucleoli		Small	Medium	Large	Usually large
	Mitoses	Few superficial				Superficial and deep
	Histological regression (see below table)		Usually		Usually not
	Percentage of atypical melanocytes		<10%	About 10 - 50%	about 50-90%	Usually> 90%

Histological regression is one or more areas within a tumor in which neoplastic cells have disappeared or decreased in number. In this case, it means complete or partial disappearance of neoplastic cells from areas of the dermis (and occasionally from the epidermis), which have been replaced by fibrosis, accompanied by melanophages, new blood vessels, and a variable degree of inflammation.

In suspected but not certain nevus or melanoma, generally perform immunohistochemistry with SOX10 (which stains cell nuclei of melanocytes), whereby melanocyte proliferation and nuclear pleomorphism is easier to see:

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  SOX10 showing dermal nevus nests.

Non-dysplastic dermal nevus on the ear with minor epidermal atypia, which on this location does not indicate dysplasia.

Report

• Diagnosis of dermal nevus.
• (Most likely grade.)

Example:

(Skin, right upper chest, shave biopsy:) Intradermal (low-grade) nevus.

  See also: General notes on reporting

Main page

• Main page of Patholines