Spindle cell melanocytic tumors

pseudoinclusions are sometimes evident and mild nuclear pleomorphism is typical. Mitoses are either absent or extremely infrequent. By definition dendritic cells are said not to be seen in this lesion. The growth pattern often presents a plexiform appearance, fascicles of nevus cells following the dermal appendages and neurovascular bundles. Perineural or endoneural extension is a very common finding. Towards the base of the lesion the nevus often adopts a single cell infiltrative growth pattern dissecting between the collagen bundles. The nevus cell population is typically admixed with densely pigmented melanophages and lymphocytic infiltrates are not uncommon. As originally described, deep penetrating nevus was not believed to be associated with any risk of recurrence or metastatic potential. The recent literature however casts some doubt on this viewpoint. Graham (8) presented one patient with a malignant variant and personal experience includes another in addition to evidence that there is a risk, albeit low of recurrence. Nuclear pleomorphism and multiple or deep mitoses are particularly worrying features. The precise nature of this lesion is also somewhat problematic. It certainly shows some overlap with blue and cellular blue nevi. Although by strict definition dendritic cells are absent, the distinction is often far from easy. Some examples of this lesion appear to represent combined nevi and both banal and Spitz variants may be encountered. Whether the dermal component represents a blue nevus variant or a true deep penetrating nevus is as yet uncertain.