Types of Microtome: Rotary, Cryostat and More

Every histology lab lives and dies by its ability to cut tissue thin enough to see through — a few microns, section after section. The instrument that does it is the microtome, and there isn't just one. Here's a quick tour of the types you'll actually meet and what each is for.

The rotary microtome

The one you picture when someone says "microtome." Turn the hand-wheel, the paraffin block advances onto a fixed blade, and out come even ribbons — usually 3 to 5 microns — of FFPE tissue. It's the routine workhorse, and honestly, section quality owes as much to the operator as the machine (see microtomy technique).

The cryostat

A microtome that lives inside a freezing cabinet, for cutting frozen tissue — above all the rapid, intra-operative frozen section. Tissue is frozen in OCT and sectioned right there in the cold. See the cryostat microtome.

The sledge (and base-sledge)

Built for the big and the tough — large or hard blocks that a rotary would struggle with. The specimen or knife rides on a track, so you can take larger sections than a rotary allows.

The ultramicrotome

A specialist that shaves sections down to the nanometre scale with a glass or diamond knife, for electron microscopy. You'll not find it in routine diagnostic histology, but it's worth knowing it exists.

So which do you need?

For routine paraffin work, a rotary. For rapid frozen diagnosis, a cryostat is non-negotiable. For oversized or stubborn specimens, a sledge helps. In practice, most diagnostic labs run a rotary and a cryostat side by side and cover almost everything.