Frozen section

A frozen section is a test used in pathology to provide a quick diagnosis of a tissue sample during surgery. It is called a “frozen section” because the tissue is rapidly frozen soon after it is removed from the body. This technique allows pathologists to examine the tissue under a microscope to identify disease, often cancer, within minutes. The primary purpose of a frozen section procedure is to help surgeons make immediate decisions about the extent of surgery needed while the patient is still under anesthesia.

How is a frozen section performed?

1. Tissue removal: During surgery, the surgeon removes a sample of tissue from the area of interest.
2. Rapid freezing: The tissue sample is quickly frozen using a cryostat, a device that keeps the temperature very low. The rapid freezing process preserves the tissue structure without the need for the usual time-consuming fixation and embedding procedures used in traditional histopathology.
3. Sectioning: The frozen tissue block is then cut into very thin slices using a microtome inside the cryostat.
4. Staining: The thin tissue sections are mounted on slides, stained with dyes to highlight cellular structures, and then covered with a cover slip.
5. Microscopic examination: The stained slides are examined under a microscope by a pathologist, who looks for abnormal cells and other signs of disease.
6. Diagnosis and communication: The pathologist communicates the findings to the surgeon, often while the surgery is still in progress, providing critical information that can influence surgical decisions, such as whether to remove more tissue, what type of surgery to perform or if any additional treatment might be necessary.

Indications for a frozen section

The frozen section procedure is most commonly used in oncologic surgery to:

• Determine if a tumour is benign (noncancerous) or malignant (cancerous).
• Ensure complete removal of a tumour by checking the margins (edges) of the removed tissue for cancer cells.
• Guide the need for further surgical intervention during the same procedure.
• Assess the status of lymph nodes near a tumour.

Limitations of a frozen section examination

While frozen section examination provides critical real-time information during surgical procedures, it has several limitations compared to traditional, formalin-fixed paraffin-embedded tissue examination. These limitations include:

• Sample quality: The rapid freezing process can cause artifacts and distortions in the tissue structure, making some cells and tissue features harder to evaluate accurately under the microscope. This can potentially lead to misinterpretation of the tissue pathology.
• Scope of examination: Due to time constraints during surgery, only a limited portion of the tissue sample can be examined. This selective examination may miss areas of disease, leading to incomplete or inaccurate diagnoses.
• Complex cases: Frozen section analysis may be less reliable for diagnosing certain types of tumors or specific pathological conditions that require more detailed examination, special staining techniques, or molecular analysis not feasible with frozen sections.
• Technical challenges: Some tissues, such as those with high-fat content, do not freeze well, making it difficult to create suitable sections for microscopic examination. This can impair the quality of the diagnosis.
• Accuracy: While generally reliable, the accuracy of frozen section diagnosis can be lower than that of permanent sections. There’s a risk of both false-positive and false-negative results, which could impact surgical decisions.
• Interpretation: The interpretation of frozen sections requires significant expertise, and there’s always a degree of subjectivity involved. Variations in pathologist experience and judgment can lead to differences in interpretation.
• Turnaround time: Although fast, the procedure still takes time, which can extend the duration of the surgery. This might not be suitable for all patients or surgical scenarios.

Despite its advantages for immediate decision-making, frozen section analysis has limitations, including the possibility of diagnostic inaccuracies due to the rapid processing of the tissue and the potential for artifacts introduced by freezing. For this reason, a more thorough examination of the tissue, using standard histopathological techniques, is usually performed after the surgery to confirm the frozen section diagnosis and provide additional information about the disease.

About this article

This article was written by doctors to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.

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