Section thickness is identical for the sliding microtome and rotary microtome under the continuous cooling device condition

To date, no report has compared section thickness (ST) between the sliding microtome (SM) and rotary microtome (RM). We used the ice pack (IP) condition, in which the paraffin block was not cooled during slicing, and a continuous cooling device (CCD) for continuous cooling during slicing. The ST was greater for the SM than the RM in the IP condition, but it was identical between the devices under the CCD condition. Thus, we used the CCD condition for subsequent studies. In formalin-fixed, paraffin-embedded (FFPE) fish sausage blocks, the ST of the tissue surface (T-surface) was significantly concaved compared to that of the paraffin surface (P-surface) for both microtomes. On the contrary, in FFPE human kidney blocks, ST did not differ between the T-surface and P-surface. Furthermore, the eosin-positive area of PAM-stained specimens was affected by ST, and the color tone of the thickest sample differed from that of the median or thinnest sample. Our data indicated that we should use CCD conditions to ensure that ST is uniform regardless of the type of microtome. In addition, for quantitative analysis, we should utilize ST measure equipment and specimens with a constant ST.