[Fat Bear Science] Freeze me during surgery? What is intraoperative freezing?

Before surgery, doctors often use a word when communicating with patients: intraoperative freezing.

Such professional medical terms usually confuse patients for a moment. “What kind of high-tech treatment is this?” “Are they freezing me during the operation?” “Do I have to walk around in the refrigerator during the operation?”...

Today, let’s talk about the magical “freezing during surgery”.

1

What is intraoperative freezing?

"Intraoperative freezing" is a representative term in the pathology department. It refers to the method of removing tissues whose nature cannot be clearly identified during surgery, and then quickly placing them in a cryogenic machine to quickly cool the tissues to a certain hardness, and then slicing them for pathological diagnosis. Because the production process is faster and simpler than paraffin slicing, it is often used for rapid pathological diagnosis during surgery.

The above statement may be too official and profound. In simple terms, in order to quickly determine the nature of the patient's diseased tissue during surgery, we need to observe the removed tissue under a microscope to see if there are any changes in cells and tissues, and then finally determine what disease the patient has. It is essentially a pathological examination. Because the specimen needs to be treated at a low temperature of about -20°C, it is also called "rapid intraoperative freezing diagnosis."

2

When is a frozen diagnosis required?

1. Clarify the nature of the lesion (is the lesion a tumor? Is it a benign tumor or a malignant tumor?);

2. Understand whether the malignant tumor has invaded the surrounding tissues and whether lymph node metastasis has occurred;

3. Determine whether there is any residual tumor around the resection site;

4. Confirm the suspicious tissue found, such as whether the tiny particles found are lymph nodes or parathyroid glands, or just fat tissue.

3

How many steps are there in frozen diagnosis?

Frozen diagnosis is roughly divided into appointment - sampling - freezing - sectioning - staining - diagnosis.

1

Appointment: The day before the operation, the surgeon will estimate whether frozen diagnosis is needed during the operation the next day based on the patient's condition. If necessary, a frozen diagnosis application form will be filled out. Of course, there are also cases where frozen diagnosis is temporarily discovered during the operation.

2

Sampling: After the specimen is delivered, the first thing to do is to check the specimen information, report the specimen properties, and measure the specimen size.

Then select one or two representative pieces of lesion tissue; if it is a tumor, the center of the lesion and the junction of the lesion and the normal tissue should be selected.

3

Freezing: Since the specimen just cut is soft, it is not conducive to subsequent slicing. Therefore, the cut tissue needs to be placed in a low-temperature freezer. The purpose is to use the low temperature to quickly freeze the specimen into an "ice lump" so that it can be cut into an ideal slice when slicing later.

4

Slicing: Place the frozen specimen in an automatic slicer. An experienced technician shakes the machine handle to slice the specimen to a thickness of less than 10μm.

5

Staining: After the frozen section is attached to the slide, it can be placed in an automatic staining machine. After going through multiple steps such as washing, staining with hematoxylin, blueing, staining with eosin, dehydration, and covering with a coverslip, a mature frozen section is completed.

6

Diagnosis: Finally, the frozen sections will be handed over to the pathologist to complete the intraoperative pathological diagnosis. The diagnosis results will be printed on A4 paper in a standardized pathology report and sent to the surgeon, laying a solid foundation for them to continue the next step of treatment.

The process of "freezing during surgery" consists of these five steps. Although it seems simple, it is of great significance. It is very important for clarifying the patient's condition and providing support for subsequent treatment.

Taking lung nodule resection as an example, intraoperative freezing can not only determine whether the nodule is benign or malignant, but also clarify whether the margins have been removed cleanly and whether lymph nodes have metastasized. The entire process from resection and freezing to issuing diagnosis results only takes about half an hour. At this time, if the lung nodule is diagnosed as benign, then the operation is complete and only suturing is required. If the lung nodule is diagnosed as malignant, it is necessary to consider whether the surrounding invaded lymph nodes have been cleaned up and whether the scope of surgery needs to be expanded.

Intraoperative freezing is like a consultation during surgery. It allows doctors to know what to do and what not to do next.

4

Several questions about intraoperative freezing

ask

How long does it take to complete a frozen diagnosis?

answer

Half an hour.

Generally, it takes about half an hour, but if you encounter a difficult case, the time to get the result may be longer.

ask

Is frozen diagnosis a panacea?

answer

Definitely not.

First of all, the quality of frozen sections during surgery is somewhat different from that of conventional paraffin sections, and the accuracy of frozen sections is about 95%. In clinical practice, only experienced pathologists (with more than 10 years of experience in clinical pathology diagnosis) can perform frozen sections.

Secondly, frozen section sampling is very limited (only a small amount of lesion tissue is selected), and sometimes local tissue is difficult to represent the entire lesion. For some difficult cases, or cases between benign and malignant lesions, intraoperative frozen section diagnosis cannot give a clear answer.

ask

Are the results of intraoperative frozen-blood diagnosis and postoperative conventional pathological diagnosis completely consistent?

answer

uncertain.

Patients often wonder: "The intraoperative frozen diagnosis clearly said that the tumor was benign, but why did the postoperative pathology say it was malignant? Is there something wrong with the hospital's technology?"

As mentioned above, the advantages of intraoperative frozen diagnosis are that it is fast and convenient, and can make a preliminary pathological diagnosis in a short time, providing an important basis for the surgeon to proceed with the operation. However, just like the quick development of photos, the quality and clarity of the photos will be greatly reduced. Therefore, the results of intraoperative frozen diagnosis will be affected by many factors.

For routine postoperative pathological diagnosis, specimens need to be taken layer by layer, and then go through multiple steps such as dehydration, embedding, slicing, staining, etc. These processes are very tedious and complicated. If a difficult case is encountered, experts from the entire department will be organized to discuss it together, and even apply for remote consultation. This is why it takes about a week to get the results of routine postoperative pathological diagnosis. This kind of report is like a high-definition photo, which usually takes several days to get, but every small detail in the photo is clearly visible. The quality of this imaging is completely incomparable to intraoperative freezing.

Therefore, it is entirely possible that routine postoperative pathological examinations may discover things that were invisible during intraoperative freezing, thus leading to inconsistent pathological diagnosis results between the two. This is a very normal limitation of human technology.

ask

Is intraoperative freezing suitable for all diagnoses?

answer

no.

There are some situations that are not suitable for frozen diagnosis. For example, biopsy can be performed before surgery to confirm the diagnosis; the specimen is too small (less than 0.2cm); bone, skin, fat, calcified tissue; lymph node biopsy diagnosis of lymphoma, and the judgment of benign or malignant based on the nuclear division of the cell; in addition, brain tissue has a high water content and requires routine paraffin section to confirm the diagnosis; orthopedics involves amputation or other radical surgery. The above situations generally require routine paraffin section to confirm the diagnosis.

In short, just like a lighthouse guiding a lost ship in the dark night, intraoperative freezing diagnosis also points out a path for surgeons and provides a solid foundation for the next step of the operation.

■

Kim Yu-ji

Researcher of the Pathology Department of the Affiliated Cancer Hospital of Chongqing University. With many years of experience in popular science, he has participated in online and offline popular science activities with the Affiliated Cancer Hospital of Chongqing University. Currently, he is the author of the public accounts of the Pathology Department of the Affiliated Cancer Hospital of Chongqing University, Earth Knowledge Bureau, Dingxiang Medical Students, etc., and the number of readers of many popular science articles is over 100,000.

Text/Fat Bear

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Chongqing Science Popularization Base/Chongqing Health Promotion Hospital

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