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How to Enhance the Quality of your Frozen Sections

How to Enhance the Quality of your Frozen Sections


The frozen sections procedure stands as one of the most challenging tasks within an anatomical laboratory, owing to its pivotal role in surgical decision-making. The diagnosis derived from a frozen section offers vital insights to surgeons, guiding them in determining the course of the operation. These examinations allow for the checking of resection margins, effectively reducing the necessity for a second surgery, which entails significant costs and heightens patient anxiety. However, this method has some limitations. Primarily, the challenge lies in operating under low temperatures. The overall quality tends to be poor and uncertain due to cell distortion, indistinct nuclear and cellular details and presence of white areas, caused by ice crystals forming in the tissue during freezing. Given its unpredictable nature, this procedure may become imperative at any moment, demanding swift execution. The short time available for making a diagnosis creates huge pressure on the operator; furthermore, ensuring the correct orientation of the tissue is crucial. Sample identification may be compromised or inaccurate due to the absence of a dedicated cassette to securely house the sample.

Frozen Sections Steps

The frozen sections process can be delineated into five key steps. Each step entails critical considerations. Through accumulated experience and gathered feedback, Milestone has identified invaluable insights and developed useful tools, allowing to refine and enhance the achieved outcomes.
  • Grossing Evaluation
  • Freezing and Embedding
  • Cutting in the Cryostat
  • Staining
  • Microscope Analysis

Freezing and Embedding

In the freezing step, the cooling technique enables the tissue to harden quickly, making it possible to cut in the cryostat within minutes. The main problem during the freezing of a sample is the formation of ice crystals, which can destroy or damage the sample’s structure, thereby complicating diagnosis. Conventional methods include:
• direct freezing in the cryostat. This method is simpler and more cost-effective, but there are some limitations regarding cryostat temperature reduction. Consequently, the freezing process takes longer and this leads to a higher likelihood of ice crystal formation.
• liquid nitrogen (-200°C). It poses risks of room saturation and is not entirely safe.
• dry ice (-70°C)
• cold isopentane (-70°C). It is both flammable and toxic.
None of these methods allow for precise temperature control of the block. Additionally, the challenging orientation and uneven sample surfaces lead to longer cutting times as a consequence.
PrestoCHILL, is Milestone solution to enhance the quality of frozen sections. This advanced cryoembedding system works at -40°C and reduces the freezing time to 30 seconds, preventing ice crystal formation. The sample is frozen with a face-down technique, that consists in the direct contact of the sample with the cold metal, giving the fastest freezing possible. The freezing workflow is further enhanced using Milestone’s Cryoembedding Compound (MCC), specially formulated with a lower viscosity that flows easily into the cryomolds and improves adhesion to the cryostat chuck.
freezing and embedding with PrestoCHILL and MCC medium


After cutting the frozen block in the cryostat, the staining of tissue sections is essential for revealing cell structure under the microscope. One approach to enhance the diagnosis of a frozen section could be to process the slide to emulate a paraffin section, which pathologists are more familiar to. Another effective method for enhancing frozen section quality is to automate and standardize the staining process. In most instances, the current practice for staining frozen sections is a manual and operator-dependent process, leading to inconsistent and substandard visualization of nuclear and cytoplasmic details.
In order to optimize this important step of the process, Milestone has introduced PRESTO PRO, an innovative processor-stainer providing a standardized and automated approach to process and stain up to 6 frozen slides simultaneously. The automated arm moves the rack with slides into and out of the vessels on a circular platform. In the initial step, the slide is immersed in heated FineFIX, Milestone’s reagent able to fix, dehydrate and clear the tissue. Thanks to the section’s thinness and the heated FineFIX, the tissue undergoes a process within seconds that mirrors the preparation of a paraffin section, which typically takes hours. Subsequently, the rack is automatically moved to next vessels for the staining step, according to the selected protocol. At the end of staining, the slide must be cover-slipped and is then ready for diagnosis.
staining with PRESTO PRO


There are various strategies that can be implemented within the frozen section process to attain high-quality results and ensure reliable diagnosis. Gross evaluation can undergo a complete innovation through the use of MacroPATH imaging system, enabling documentation and remote control by pathologist. Freezing with PrestoCHILL through the face-down technique in a cold metal mold with lower-viscosity medium reduces the formation of ice crystals and facilitates easier and faster sectioning in the cryostat. The processing of thin sections and the automation of staining protocol with PRSTO PRO further enhance the superiority of the results, while the use of a remote microscope, along with remote control of gross evaluation, enables frozen examinations even when the pathologist is not physically present in the laboratory.

Want to know more?

Watch our educational Webinar “How to Enhance the Quality of your Frozen Sections”
Our Specialist discusses the current frozen sections techniques, highlighting its limitations and challenges. Through live streaming from our laboratory, we will unveil strategies that pathologists and technicians can implement to elevate their frozen sections, transforming this procedure into a reliable and quality method.

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