Case 43 Male, 7 years. Papule, skin of upper armShow diagnosis & comments
BLITZ NAEVUS is the slightly 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 the 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.
This particular case shows more features of Spitz naevus NOS than of 'Blitz naevus', but the deep dermal penetration with a wedge shape and with retention of some pigment production in the deep part could be cause to call the lesion a Blitz naevus. Obviously the only diagnostically important here is the fact that this divergence from what is usually seen in Spitz naevus should not lead to a suspicion of malignancy.