Skin tissue can be processed on several different programs, based on tissue size, thickness, and characteristics. The table below is a quick reference guide for processing skin specimens. Processing times will vary and are heavily dependent on the type of processor, temperature, and reagent combination. The times listed below are for a closed system (non-microwave) processor that utilizes graded alcohols and xylenes.
| Small shaves, punches, scrapings, nails | Thin, brittle; each piece less than 4 mm X 2 mm thick | Biopsy or rapid - 5 to 7 hours |
| Large shaves, small excisions | Minimal fat; less than 3 mm thick | Routine - 7 to 10 hours |
| Large excisions, cysts, lipomas | Fatty; tissue sections are almost edge to edge in cassette, less than 4 mm thick | Extended - 10 to 13 hours |
The length of the processing schedule is directly related to tissue size/thickness and fat content. Small and brittle skin tissue will be overly dehydrated and hardened by a long processing schedule. Sectioning of dry tissue is more difficult. On the other hand, a large excision that shows a deep fatty margin will NOT be dehydrated and infiltrated completely on programs with rapid dehydration, clearing, and infiltration schedules. Fat is very difficult to process, even with vacuum processors. Extended processing times (as well as freshly rotated reagents) ensure proper processing of large, fatty samples. In the image, fatty skin sections that were under-processed are shown exploding on a warm water bath. Inadequately processed skin is nearly impossible to section and may need to be reprocessed. In order to save time and resources, fatty tissue should be processed on extended programs from the start.
