[Unusual variants of blue naevi--a report of four cases (author's transl)].

This paper presents four unusual variants of blue naevus: a giant-sized blue naevus, a blue naevus assuming the clinical and histological appearance of a histiocytoma, a plaque-type blue naevus, and a pedunculated cellular blue naevus. Two of these lesions were studied at the ultrastructural level: in one case the dermal melanocytes contained malanosomes of all stages, thus documenting active melanin synthesis. In the other lesion, melanocytes of identical appearance were found in the superficial portions, whereas inactive melanocytes, densely packed with mature melanosomes, predominated in the deeper portions. It is concluded that blue naevi may vary considerably, both clinically and in histological appearance, as well as in regard to melanin synthesis activity.