After cancer surgery, the key question is whether there are any cancer cells left behind that can continue to grow or whether the entire tumor has actually been removed. To find out, the tumor is examined in the pathology department. Previously, thin sections were made which were then analyzed under a microscope. A new technique, developed at the TU Vienna together with the TU Munich, is now set to revolutionize pathology: It has succeeded in making tumor tissue transparent and illuminating it with a special ultramicroscope. This allows the entire removed tissue to be analyzed in 3D without the need for an incision. This should significantly increase the reliability of the diagnosis. The new technique has now been published in the journal "Nature scientific reports".
Under the microscope, it is possible to see whether the removed tumor is surrounded by a margin of healthy tissue. The tumor is then said to have been removed from healthy tissue. If this is the case, the patient often only has to recover. If this is not the case, the patient may have to undergo further surgery or additional radiotherapy. This is particularly common after breast cancer surgery. The problem with this is that it is never possible to examine the entire tumor in this way. Usually, an incision about 4 micrometres thick is made every 5 millimetres. This means that only about one thousandth of the entire tumor volume is actually examined. In critical areas, the thin sections can also be made narrower, but the entire tissue cannot be captured in this way.
However, with the help of a special technique known as ultramicroscopy, it is now possible to make the entire tumor visible in three dimensions - something Inna Sabdyusheva worked on as part of her dissertation (at the Vienna University of Technology and MedUni Vienna's Center for Brain Research). She developed a chemical process that can be used to "clear" breast cancer samples - they become transparent, but the structure remains unchanged and the cancer cells can still be recognized.
The transparent sample is then examined under an ultramicroscope. A so-called "light sheet", a thin layer of laser beams, penetrates the tissue. This is used to analyze the sample layer by layer, and any sections through the tumor can then be displayed on the computer, even though the tumor itself has never been cut. This provides insights that were previously impossible: In some tissue samples, for example, it was possible to recognize milk ducts that were clogged with cancer cells.
The chemical process on which Inna Sabdyusheva's work is based was developed at the Vienna University of Technology by Klaus Becker. A special optical system, with which particularly long and thin light sheets can be produced, was constructed in the same working group by Saideh Saghafi. This was crucial for the current work - the resolution of this microscopy method depends on how thin the light sheet is.
The investigations were carried out in close collaboration with the Institute of Pathology at the Technical University of Munich, which also provided most of the tumor pieces from breast cancer operations. The Department of Surgery at Vienna General Hospital also provided pieces from other types of tumors.
The new 3D method may also provide completely new insights into cancer development in the future. As it is now possible for the first time to visualize the spread of cancer cells in human surgical specimens in three dimensions, the understanding of tumour biology should also make significant progress.
The new 3D tumor microscopy should make work in pathology much easier. Instead of inspecting a large number of histological sections under the microscope, pathologists will in future be able to scroll through the images on the screen with the mouse, similar to radiology. Dodt believes that the huge amount of image data generated in the process will also open up completely new opportunities in the field of artificial intelligence: perhaps in the future their programs could speed up and simplify tumor diagnostics.
Source: TU Vienna
