A Comparative Analysis of Optimal Cutting Temperature (OCT) Compound and Water as Embedding Media in Frozen Section

The commonly used embedding medium in frozen section is a commercially available optimal cutting temperature (OCT) compound, which is a water-soluble mixture of glycols and resins. However, its high cost limits its widespread use in laboratories with limited resources. In the present study, we compared two embedding media (OCT compound & Water) based on the mean freezing time and effect on the quality of section in terms of staining and the presence of freezing artifacts in different types of tissues.

Fresh & unfixed specimens from 45 cases were analysed prospectively. The specimens included mucosal margin assessment (n=15), lymph node metastases (n=16), and fatty tissues (breast lumpectomy) for margin assessment (n=14). Average freezing time, presence of freezing artifact (extensive, minimal, or absent) and quality of nuclear and cytoplasmic staining (good, satisfactory, or poor) were noted.

Overall mean freezing time was marginally lower for OCT (3`34`) when compared to water. (3`58`) Lymph nodes took the shortest time to freeze irrespective of the embedding medium used. Fatty tissues took the longest time to freeze with water (4`12`) as compared to OCT (3`35`). With OCT, the mean freezing time was lowest for lymph nodes (3`22`) and highest for mucosal margins. (3`45`) Extensive freezing artifacts were more commonly observed with OCT than water. (37.8% vs 31.1% respectively) Staining quality was comparable for both embedding media overall and amongst the different types of tissues.

In settings where cost is a limiting factor, water can function as a cheaper and readily available embedding alternative to OCT. In frozen sections involving fatty tissues where time is a limiting factor, OCT provides a shorter mean freezing time and can be used in place of water.