New double embedding technique for specimens of endoscopic submucosal dissection using agarose: comparison with other...

Procedure of endoscopic submucosal dissection (ESD) has been introduced widely for treatment of early gastric cancers. For such specimens, accurate pathological diagnosis, especially concerning depth of the invasion and exposure to margins, is essential to decide on the necessity of additional treatment. Therefore, easy and reliable tissue-processing method for multiple cut specimens is needed. The authors report here a new double embedding technique for specimens of ESD.

Formalin-fixed whole specimen was superficially wrapped by agarose (the first embedding), and the tissue-agarose block was cut at 2-3 mm intervals. Each cut specimen was laid down with 90° rotation. This procedure permitted 'on edge' embedding of thin tissues in paraffin (the second embedding) and subsequent preparation of perpendicular section to the tissue surface. The authors compared the handleability and stainability among several media including various types of agar, agarose and gelatin for first embedding. A survey by questionnaire was carried out on handleability and/or impression on various tissue-processing steps from pathology technicians.

Among the media examined, agarose showed the best solubility in water and the best transparency on several representative stainings. According to the survey, pathology technicians seemed to feel that the present method was better than the usual tissue processing method, especially in shortened time consumption and accuracy of alignment of multiple tissues for ESD specimens.

The present new double embedding technique using agarose provides not only an easy and reliable embedding procedure for technicians but also accurate and exact diagnosis for pathologists.