Reflected light microscopy, step-by-step diagnostics for the differentiation of small pigment cell tumours

General information
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The dermatologist in the polyclinic and practice is often confronted with small pigment cell tumours which are difficult to classify clinically. In addition, about 20% of the malignant melanomas and initial melanoma metastases to be differentiated are smaller than 6 mm in maximum clinical diameter. Since the limited resolving power of the eye hardly allows a diagnosis from a tumor diameter of 5 mm and below, the use of the reflected light microscope is useful in these cases. The respective histological correlate can largely be interpreted from the characteristic incident light features and the architectures of the lesion projected into the skin plane. A practice-proven step-by-step protocol is used for orientation.

Literature
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Bergman R et al (1992) Malignant melanomas with histologic diameters less than 6 mm. J Am Acad Dermatol 26: 462-466
Neuber H et al (1991) Non-diagnosable malignant melanomas. Dermatologist 42: 220-222
Paul E (1991) Problem of the clinical and histological classification of early forms of malignant melanoma. In: Meigel W, Lengen W, Schwenzer G (Eds.) Diagnosis & Therapy of malignant melanomas. Diesbach, Berlin, S. 106-119
Schulz H (1997) Reflected light microscopic characteristics of small malignant melanomas. dermatologist 48: 904-909
Shaw HM, McCarthy WH (1992) Small diameter malignant melanoma: a common diagnosis of New South Wales Australia. J Am Acad Dermatol 27: 679-682
Zalaudek I (2005) Dermoscopy for challenging melanoma; how to raise the 'red flag' when melanoma clinically looks benign. Br J Dermatol 153: 200-202

Tables
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Level		Characteristics
Level 1	Rather benign pigment cell tumors	Zone, coccard-like or radial-strictive base architecture
		Area with greyish-black centropapillary globules, ring-shaped or centrole lesional
		Peripheral grey-blue pseudopodia, isolated or annular

Level 2	Benign/malignant pigment cell tumours	Abrupt pigment breaks off in the trabeculae
		Peripheral brown/black dots
		Perivasal melanophages
		Inverse (negative grid pattern)
		Brown/black dot on blue/grey background
		Regression zones with marginal melanophages

Level 3	Rather malignant pigment cell tumors	At least 2 Level 2 characteristics
		Periläsional erythema from ectatic capillaries
		Intra- or perilesional grey pigment densifications
		Pseudopodia-like marginal zone
		Areas with centropapillary globules
		Perifollicular grey-black pigment rings
		Radial streaming
		Blue-in pink area
		Melanophagus pseudotrabecula (face)
		Melanophagus trabecula diffusely distributed over the lesion
		Alabaster-like lacunae

Level 4	Malignant pigment cell tumors with high probability	At least 2 characteristics from level 2 or level 3
		Blue-white veil
		Deeply localised grey-blue or grey-brown mesh fragment
		Whitish or bluish-opaque septa
		Microscopic blood lakes (microhaemorrhages)
		Basic pattern of polymorphic and/or aneurysmatic vessels
		Areas with polymorphic and/or horizontally extending dilated vessels
		Saccular pattern (red-blue, red-light brown, reddish-brown, blue-grey)
		Lesion surrounded by grey stripes (intravascular melanoma cell infarctions)