What is EBUS-TBNA, and why is it used?

EBUS-TBNA, or Endobronchial Ultrasound-Transbronchial Needle Aspiration, is a minimally invasive procedure used to obtain tissue samples from the mediastinum, which is the space in the chest between the lungs. It's significant because it allows doctors to diagnose various conditions such as sarcoidosis, infections, lymphomas, and cancers that may have spread from other parts of the body. The technique is valuable as it provides a way to gather cells for further examination without the need for more invasive surgical procedures.

What is ThinPrep, and why is it used in diagnostic testing?

ThinPrep is a liquid-based preparation technique used to prepare cells collected during procedures like EBUS-TBNA for microscopic examination. It's important because it provides a standardized and consistent way to view cells, aiding in the detection of abnormalities. However, it may not always capture larger tissue fragments as effectively as other methods, which is why it is often used in conjunction with cell block preparations for a more comprehensive analysis.

What are cell blocks, and why are they important in diagnosing diseases?

Cell blocks are preparations made from cell samples that allow for more in-depth analysis compared to direct smears or liquid-based preparations like ThinPrep. Cell blocks are significant because they enable additional studies such as immunohistochemistry, genetic testing, and molecular analysis. This is particularly crucial for targeted therapies. Different methods of preparing cell blocks, such as plasma-thrombin, HistoGel, and CellGel, can affect the quality and quantity of diagnostic material obtained.

What are granulomas, and why is it important to detect them?

Granulomas are small clumps of immune cells, specifically epithelioid histiocytes, that form in response to inflammation or infection. Detecting granulomas is important because their presence can indicate conditions like sarcoidosis or certain infections. The size and number of granulomas can provide valuable information for diagnosis. Different preparation methods, such as cell blocks versus ThinPrep slides, can impact the ability to detect and accurately measure granulomas.

What are plasma-thrombin, HistoGel, and CellGel, and why are they used in cell block preparation?

Plasma-thrombin, HistoGel, and CellGel are three different methods used to prepare cell blocks from tissue samples. Plasma-thrombin and CellGel appear to be more effective in yielding diagnostic material compared to HistoGel. The choice of method can impact the ability to detect and analyze granulomas, ultimately affecting diagnostic accuracy. Selecting the optimal cell block preparation method is crucial for obtaining comprehensive and reliable results.

Microscopic slide transforming into a field of granulomas.

Cell Block Showdown: Finding the Best Way to Spot Granulomas

Samir D’Costa in Health & Wellness December 2025 • 4 min read.

"A new study compares different cell block methods used with ThinPrep slides to detect granulomatous disease, focusing on effective diagnostic techniques."

When doctors need to figure out what’s going on in the mediastinum (the space in your chest between your lungs), they often use a technique called EBUS-TBNA. Think of it as a minimally invasive way to take samples for testing. This method is especially useful for detecting diseases like sarcoidosis, infections, lymphomas, and even cancer that has spread from other areas of the body.

EBUS-TBNA allows doctors to collect cells, which can then be prepared in a few different ways for examination. These include direct smears, liquid-based preparations like ThinPrep (TP), and cell blocks (CBs). Each method has its pros and cons, and labs often pick the one that works best for them based on their specific needs and resources. Cell blocks, in particular, can be really helpful because they allow for additional studies like immunohistochemistry, genetic testing, and molecular analysis—all crucial in the age of targeted therapies.

In a recent study, researchers set out to compare three different cell block preparation methods: plasma-thrombin, HistoGel, and a modified version of HistoGel called CellGel. They wanted to see which method, when used with ThinPrep slides, was most effective at finding granulomas (small clumps of immune cells) in samples taken from patients with mediastinal granulomatous disease. This research is all about finding the best way to improve diagnostic accuracy using minimally invasive techniques.

Plasma-Thrombin vs. HistoGel vs. CellGel: Which Method Wins?

Microscopic slide transforming into a field of granulomas.

The study looked back at 264 specimens taken from 124 patients who had undergone EBUS-TBNA for suspected granulomatous disease. After the ThinPrep slide was made, any material left over was used to create a cell block using one of the three methods. The researchers then carefully counted and measured the granulomas on each preparation using digital software. Granulomas were defined as a cluster of at least five epithelioid histiocytes clumped together.

The results showed some clear differences between the methods:

Cell Blocks Excel: Granulomas were spotted on cell blocks in nearly 19% of cases, but only on ThinPrep slides in about 5%.
More and Bigger: All three cell block methods found significantly more and larger granulomas compared to the ThinPrep slides.
Plasma-Thrombin and CellGel Lead: Plasma-thrombin and CellGel methods seemed to yield more diagnostic material compared to HistoGel.
Numbers Don’t Lie: On average, ThinPrep slides showed 4.0 ± 0.4 granulomas, while cell blocks showed 15.3 ± 1.1. Granuloma size averaged 119.2 ± 3.2 µm on ThinPrep slides versus 271.8 ± 7.3 µm on cell blocks.

Statistical analysis confirmed that the plasma-thrombin and CellGel methods had a higher granuloma yield than the HistoGel method. Moreover, cell blocks, in general, showed more numerous and larger granulomas compared to ThinPrep slides. This suggests that relying solely on ThinPrep slide evaluation might lead to overlooking larger tissue fragments obtained during needle aspirations.

Why This Matters for You

This study highlights the importance of using cell block preparations in addition to ThinPrep slides when evaluating samples for granulomatous disease. The plasma-thrombin and CellGel methods appear to be particularly effective at capturing granulomas, potentially leading to more accurate diagnoses. This could mean fewer missed cases and better outcomes for patients undergoing evaluation for mediastinal granulomatous disease. Future research may explore whether these findings apply to other types of lesions and specimens, further refining diagnostic techniques in cytology.