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

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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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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  1. Bergman R et al (1992) Malignant melanomas with histologic diameters less than 6 mm. J Am Acad Dermatol 26: 462-466
  2. Neuber H et al (1991) Non-diagnosable malignant melanomas. Dermatologist 42: 220-222
  3. 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
  4. Schulz H (1997) Reflected light microscopic characteristics of small malignant melanomas. dermatologist 48: 904-909
  5. Shaw HM, McCarthy WH (1992) Small diameter malignant melanoma: a common diagnosis of New South Wales Australia. J Am Acad Dermatol 27: 679-682
  6. 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)

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Last updated on: 29.10.2020