A new laboratory device with mathematically based positioning of a frozen tissue block facilitating precise sectioning of large specimens.

Abstract

Mohs micrographic surgery (MMS) is a treatment method aiming at thorough, personalized eradication of skin cancers by mean of staged excision of tissues surrounding the tumor with complete (100%) histopathological examination of their margins. In many MMS laboratories, the excised tissue is divided, shaped, frozen in a cryostat with a heat extractor and positioned manually (with the block on the object disc) in an articulated cryostat chuck during cutting. However, these activities may be difficult, time-consuming and associated with the risk of imprecise tissue sectioning. Development of a laboratory device allowing for processing of large tissue specimens, with the function of mechanical, mathematically steered positioning of the tissue block surface directly to the microtome knife cutting place, eliminating the need for manual adjustment. The prototype device was designed and manufactured. Its functioning was tested on 513 histological slides produced during 212 operations of skin cancers using MMS. The depth of the first complete sections and the diameter of sections were measured. Complete sections were obtained at an average depth of 81.60 m (min. 20 m, max. 180 m, SD = 29.15), whereas the average diameter of sections was 18.11 mm (min. 4 mm, max. 42 mm, SD = 9.10). The histological processing of large specimens with mathematically based positioning of the tissue surface in relation to the cryotome knife cutting plane is precise, fast and easy. The device can be useful in those MMS centers which continue to employ manual setting of the cryostat chuck or share the cryostat with other users, which prevents fixing the chuck position (including large hospital settings). It may also be helpful in centers using a cryostat with a fixed chuck, for the correction of minimal inaccuracies of its preset position.