The application of toluidine blue staining in intraoperative cell imprint and frozen section rapid freezing diagnosis

When a surgeon is operating, the clock is ticking. If a patient has a tumor, the surgeon needs to know immediately whether it is cancerous and whether the edges of the removed tissue are clean. This decision often happens while the patient is still on the operating table. To get this answer, a pathologist takes a tiny piece of the fresh tissue, freezes it, and stains it with a dye so it can be seen under a microscope. The most common dye used for decades is a combination of two chemicals that turn cell nuclei blue and the surrounding material pink. This method is reliable, but it takes time and requires careful handling. In recent years, a different, older dye called toluidine blue has been revisited. This dye is known for staining cell nuclei a deep, sharp blue very quickly, but it does not show the surrounding cell details as well. The question for modern medicine is whether this faster, simpler dye can replace or supplement the traditional method without sacrificing the accuracy needed to save a life.

Researchers at hospitals in Kunming, China, set out to answer this question with a direct comparison. They gathered tissue samples from 348 patients undergoing surgery for various conditions, including tumors in the breast, lung, uterus, and thyroid. They did not just look at one method; they tested four different ways of preparing and staining these tissue samples side by side. The first method was the traditional way, done by hand with the standard blue-and-pink dye. The second was the same standard dye but processed by a machine to ensure consistency. The third method involved freezing the tissue and staining it with the fast-acting toluidine blue. The fourth method was even quicker: instead of cutting a thin slice of frozen tissue, the researchers pressed the fresh, cut surface of the tissue directly onto a glass slide to leave an imprint of the cells, then stained that imprint with toluidine blue. They then compared how long each method took, how clear the images looked, and how often the diagnosis matched the final, confirmed result from the standard lab test.

The results showed a clear trade-off between speed and detail. The toluidine blue cell imprint was by far the fastest, taking anywhere from less than half a minute to just under four and a half minutes to complete. This was significantly quicker than both the hand-stained and machine-stained traditional methods, which took nearly seven minutes and six minutes respectively. However, speed came with a cost in visual quality. When the researchers rated the images based on how well the cells looked, the machine-stained traditional method produced the best results, followed closely by the hand-stained version. The toluidine blue frozen sections were slightly less clear, and the toluidine blue cell imprints were the least clear of all. The main issue with the toluidine blue method was that while it painted the cell nuclei with intense, sharp detail, it left the rest of the cell looking somewhat vague. It was excellent at showing the nucleus, which is the control center of the cell, but poor at showing the cytoplasm, which is the body of the cell. This lack of detail made it harder to distinguish between different types of benign, or non-cancerous, growths.

Despite these visual differences, the diagnostic power of the methods told a more nuanced story. When it came to identifying cancerous, or malignant, tumors, all four methods performed equally well. Every single method correctly identified malignant lesions with an accuracy rate exceeding 95 percent. In these cases, the sharpness of the nucleus provided by the toluidine blue was enough for the pathologist to make the correct call. However, the story changed when looking at benign tumors or non-cancerous tissue. Here, the traditional methods, whether done by hand or machine, were significantly more accurate. The toluidine blue cell imprint, in particular, struggled to tell the difference between harmless growths and normal tissue. Because of this, the researchers concluded that while the toluidine blue cell imprint is not reliable enough to serve as an independent definitive diagnosis for benign conditions, it remains qualified for rapid intraoperative diagnosis of malignant tumors. It is best used as a rapid screening tool specifically for identifying malignant lesions.

The study suggests a practical path forward for operating rooms. The traditional machine-stained method remains the gold standard for the highest quality images and the most reliable diagnosis across all types of tissue. However, the toluidine blue frozen section offers a very good balance, providing reliable results for most cases while being faster than the traditional hand-stained method. The toluidine blue cell imprint, with its extreme speed, serves a different purpose. It is not a replacement for the full diagnosis of benign conditions but acts as a rapid triage tool for cancer. If a surgeon needs to know in under five minutes whether a suspicious lump is likely cancer, the toluidine blue imprint can provide that answer quickly. If the result is positive for malignancy, the surgeon can proceed with confidence. If the result is negative, or if the tissue looks benign but the imprint is unclear, the team can then rely on the more detailed, traditional methods to confirm the final diagnosis. This approach allows medical teams to use the right tool for the specific moment, balancing the need for speed with the absolute necessity of accuracy.