Table 1: Essential features.

Features	Properties	References
Asymmetry	asymmetry index	[27, 32, 40, 57, 62, 65, 130, 252, 253, 291, 298, 336, 344, 363, 382, 387, 388]
	circularity factor	[40, 51, 62, 267, 291, 337, 344, 349, 366, 382, 386, 388-391]
	skewness	[103, 392]
Border irregularity	edge abruptness	[57, 65, 130, 252, 291, 351]
	lesion areas and perimeters	[62, 252, 253, 337, 363, 366, 367, 379, 382]
	radial distance	[267, 369]
	bounding box	[267, 344, 369, 377, 382, 390]
	mean and variance of lesion boundary magnitude	[40, 57, 337, 344, 366, 393]
Border Sharpness	compactness index	[27, 57, 65, 252, 337, 344, 351, 379, 382, 394]
	fractal dimension	[48, 57, 65, 96]
Colour	colour homogeneity	[51, 57, 65, 252, 347, 351, 363]
	island of colour	[40, 51, 58, 103, 130, 366, 382, 391]
	colour histogram	[28, 64, 198, 292, 299, 345, 366, 370, 376, 377, 379, 382, 395-398]
	RBG statistics (such as ratio, chromaticity, spectral)	[57, 103, 252, 253, 291, 337, 344, 367, 382, 385, 392, 393]
Diameter	lesion diameter	[51, 57, 168, 252, 344, 369]
Differential Structures	pigmented network (typical/atypical)	[17, 21, 28, 52, 58, 93, 94, 121, 127, 190, 242, 291, 347, 358, 371, 373, 376, 399-406]
	homogeneous areas	[61, 382, 407]
	branched streaks globules	[17, 52, 93, 94, 345, 400, 405, 406, 408]
	structure-less areas (such as dots, globules, blotches)	[17, 52, 93, 94, 121, 291, 345, 357, 358, 376, 400, 402, 405, 406, 408-410]
	blue-white veil	[17, 52, 58, 121, 291, 372, 400, 403]
Lesion Surface Structures	co-occurrence texture features	[40, 48, 51, 103, 291, 344, 347, 351, 366, 369, 376, 382, 386, 391, 392]
	wavelet texture features	[62, 64, 336, 386]
Other features	correlation index between geometry and photometry	[57, 65]
	sonography characteristics, hypo-echogenicity	[57, 108, 177, 411, 412]