Case 42 Female, 11 years. Papule, skin of lower legShow diagnosis & comments
BLITZ NAEVUS is the somewhat playful name that is sometimes used for lesions that combine the istological features of Spitz naevus and those of a blue naevus variant, such as deep penetrating naevus. The upper part of the lesion shows features of Spitz naevus (large oval or spindled cells; junctional nests with some shrinkage artifacts; enlaged somewhat vesicular nuclei) whereas deeper parts do not show the gradual diminuition in cellularity, cellular and nuclear size, absence of pigmentation and mitotic activity that is characteristically seen in Spitz naevus. Rather the deep part shows features of deep penetrating navus, with small clusters of slightly pigmented largish cells that lie between preexistent dermal structures, the deepest extension often being around a hair follicle, resulting in a wedge shape. The upper and lower part of the lesion seem to merge with one another; there are no two distinct components as in combined naevi (featuring a 'blue' and a 'non-blue' component; see slide set of blue naevi).