Exceptions to rules & mimickers

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 Author(s): Ashfaq A. Marghoob, Ayelet Rishpon

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Description	The two-step dermoscopy algorithm aims to differentiate between melanocytic and non-melanocytic lesions and to determine if a melanocytic lesion is benign or malignant. While algorithms serve as guidelines that apply to the majority of cases, one should remember that every rule has exceptions. The recognition of the exceptions is essential for the maintenance of high diagnostic precision.
Author(s)	Ayelet Rishpon · Ashfaq A. Marghoob
Responsible author	Ash Marghoob → send e-mail
Status	unknown
Status update	March 5, 2018
Status by	Ralph P. Braun

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Feature	Differential Diagnosis	Mimickers
Negative Network	Melanoma	Ridges of Seborrheic keratoses
	Spitz/Reeds	Globular Structures of dermatofibromas
	Severe Dysplastic nevi
	CMN
Streaks	Melanoma	Leaf-like areas of BCC
	Spitz/Reeds nevus	Ridges (fat-fingers) of seborrheic keratoses
	Pigmented periphery of Bowen's disease
	Pigmented periphery of cutaneous mets
Network	Nevi	Fingerprinting of solar lentigines
	Melanoma	Cerebriform pattern of seborrheic keratoses
	Solar lentigo
	Ink spot lentigo
	Dermatofibroma
	Accessory nipple
	Mastocytosis
Globules	Nevus	Lacuna
	Melanoma	Ovoid nests
	Clonal Seborrheic keratosis	Blue-gray ovoid nests
	Cutaneous metastasis	Pigmented cysts
		Comedo-like openings
Peppering/granularity	Melanoma	Blue-gray dots of BCC
	Lichen planus-like keratosis	Linear brown dots of pigmented Bowen’s disease
	Pigmented actinic keratosis
	Nevi (focal and limited)
Vessels	Various melanocytic and non-melanocytic lesions	Small ulcerations as in superficial BCC
	Linear brown/red dots of pigmented Bowen’s disease
	Red globules of BCC
	Background vessels in normal skin and sun-damaged skin
Blotch	Melanoma	Subcorneal hemorrhage
	Clark's nevi	Thrombosed angioma
	Blue nevus	Black lamella
	Reed's nevi	Exogeneous pigmentation
		Heavily pigmented seborrheic keratoses
		Heavily pigmented BCC
		Venous angiomas
Shiny-white streaks	Melanoma	Negative network
	Spitz nevus	White lines of scalp nevi
	BCC	Wickham striae
	Dermatofibroma	Rail lines (pyogenic granuloma)
	Scar
Circles-white	Actinic keratoses	Milia-like cysts
	SCC	Lobules of sebaceous hyperplasia
		White clods of BCC
		Lacunes of lymphangiomas
		White globules of balloon cell nevi
		Folliculitis
		Molluscum
Circles-brown	Dermatofibroma	Curved lines of solar lentigines and seborrheic keraotoses
	Bowen's disease	Comedo-like openings
	Facial melanoma
	Facial nevi
	Facial solar lentigines
Angulated lines	Melanoma of sun-damaged skin	Spoke-wheel areas
	Pigmented actinic keratosis	Fingerprinting
	Lichen planus-like keratosis	Prominent network of congenital nevi and Clark's nevi
		Prominent lines of ink spot lentigo
		Lattice like pattern of acral nevi