Neural spectrum: palisaded encapsulated neuroma and verocay body poor dermal schwannoma.

We examined 25 palisaded encapsulated neuromas (PEN) of the skin and used peripherin antibody as an immunohistochemical label for axons. Quantitative analysis of the axon to schwann cell nuclear ratio for each PEN was determined by examining cross-sectioned neuroid fascicles. This revealed that 120 of the 253 cross-sectioned fascicles in PEN lacked axon and only 5% of the fascicles had an axon to schwann cell nuclear ratio greater than 1:2. In contrast, all fascicles in 40 dermal nerves adjacent to PENs as well as 35 traumatic neuromas in surgical scars had an axon to schwann cell nuclear ratio of at least 1:2 and the majority a ratio of 1:1 or higher. These results suggest that there is a spectrum between PENs which are axon rich to a form of schwannoma with an identical histopathology which lacks significant axonal content and that not all PENs are true neuromas.