Nail Unit Specimens.

Histologic submission and processing of nail unit specimens require special attention, primarily because of the contrast between the hard plate and the delicate matrix/bed tissue. Adherence of the plate to the glass slide is particularly challenging, and a protocol is included to address this challenge. Loss of the often small, fragile matrix/bed tissue can lead to absence of histopathologic features needed to make a definitive diagnosis. Of primary importance is the submission of matrix/bed specimens, which are often small and fragmented on a paper template of a nail, which is then placed securely in a tissue cassette between sponges, thereby preserving tissue orientation and allowing for flat fixation for a minimum of 8 h. Immunostains and other special stains also differ somewhat from their use elsewhere on the skin, the details of which are presented.