"Tubular Spitz's nevus" an artifact of fixation?

Spitz's nevi may contain numerous tubule-like structures. This phenomenon has been described as "tubular Spitz's nevus" and has been attributed to either apoptosis in the center of nests of melanocytes or tubular metaplasia of melanocytes.

In order to study this peculiar phenomenon, we reviewed 31 Spitz's nevi from our teaching collection.

Empty spaces vaguely resembling tubules were found in 15 Spitz's nevi, all of which were examples of the epithelioid-cell type of Spitz's nevus. Histopathologically and immunohistochemically, there was no evidence of apoptosis within or around tubule-like structures. Empty; spaces in the center of nests ranged from distinctive tubule-like structures to only slight separation of melanocytes from one another. Furthermore, empty spaces were also seen around nests, often in combination with distinctive tubule-like changes.

Our findings suggest that so-called "tubular" structures in epithelioid Spitz's nevi result from retraction of tissue secondary to fixation in formalin. "Tubular Spitz's nevus" seems to represent an artifact rather than a distinctive variant of Spitz's nevus.