Sean Klepper M.D.
Artur Zembowicz M.D....
- Peak incidence in the third decade; slight female predominance
- Most common on the extremities
- Presents as a small, symmetric, sharply demarcated, pigmented papule or nodule of acute onset
- The importance of recognizing this entity lies in the fact that it is often misdiagnosed as melanoma.
- Junctional or compound nevus (with the junctional component often predominating)
- The lesion displays a symmetric configuration with fairly sharply demarcated lateral borders.
- The nevus cells are uniform spindle cells arranged in tightly packed fascicles, with relatively uniform spacing between the fascicles and with the cells often vertically oriented.
- The spindle cells tend to be narrower than those of classic Spitz nevus, and have nuclei smaller than or equal in size to keratinocyte nuclei and inconspicuous nucleoli.
- The nevus cells typically contain at least focall abundant coarse melanin pigment, in contrast to Spitz nevus. The pigment may also be present within the keratinocytes and the papillary dermis.
- The nuclei of the nevus cells become smaller as one procedes deeper into the lesion (they "mature").
- Mitoses are often present in the junctional component, but are rare to absent in the dermal component.
- Pigmented spindle cell nevus and Spitz nevus exist along a spectrum, and one sometimes encounters lesions with features intermediate between the two entities.