Reflected light microscopy, pseudopodia-like marginal zone

Peripheral tumor outgrowths projected into the incident light plane, pointing radially, are bulbously thickened at the ends, multi-fingered, laterally bent and sometimes tree-like.

Incident light microscopy: The peripheral tumor extensions, which are thickened at the ends and finger-shaped, are blue-grey or brown-grey in colour. In inflammatory neoplastic vascular reaction the pseudopodia are surrounded by a red rim.

In the group of pigment cell tumors, the specificity of this reflected light microscopic feature for malignant melanomas is over 90%, the sensitivity is 18%. Occasionally, spindle cell nevi show the phenomenon.

Confluent junctional melanocyte nests proliferate peripherally into the papillary stratum and into the border area of the reticular stratum. Partially strong transepidermal pigment discharge.