What is histopathology?

By Prerna Roy & Victor Tsang

Introduction 

Tissues, diseases, images, and dyes – the field of histology seems to find a way to connect all these different aspects that demonstrate modern medicine's profoundness. This post will cover the key steps in creating a histological image, their importance in diagnosis, and what PhoMedics is contributing to this ever-important field.

 

Histopathology is a field dedicated to studying diseases by examining tissues and cells under a microscope. These images captured offer a myriad of biological information, from cellular details to structural distributions, which to untrained eyes, seems to be just an array of cells; but to the specially trained experts, called histopathologists, these images are valuable evidence for them to examine and make life-saving diagnoses. This field is particularly important for helping us diagnose diseases that may only be seen at the cellular level, including but not limited to autoimmune diseases, inflammatory diseases, and cancer. In the following article, we will embark on the journey of understanding the basics of histopathology and how PhoMedics is improving the whole process with CHAMP technology.  

 

How are histological images made? 

There are some key differences between histological images and ordinary microscopy images of tissues. Tissues on a glass slide will appear dull grey due to a lack of contrast, making it impossible to visualize cellular features. Thus, histological images make use of various dyes and stains to better visualize cellular features to obtain an accurate diagnosis. These dyes exploit the biochemical differences of tissue to produce differentially coloured components. One of the most common stains is haematoxylin and eosin (H&E), which are used particularly to highlight the cell nucleus and outline the cell’s morphology. This information is some of the key perimeters for the pathologist to diagnose cancers. 

 

The overall procedure can be segmented into five key steps: fixation, processing, embedding, sectioning, and staining. These steps are the gold standard procedure used to obtain histological images – it is the global standard set within the medical field. In particular, H&E is an important stain for human tissue samples aiding the diagnosis of cancers and other diseases. After this procedure, the image is interpreted and a diagnosis is made so that patients can begin their treatments or amend any ongoing treatments. 

 

Why are histological images important for cancer diagnosis? 

Histopathologists often make the initial and ongoing assessments of diseases such as cancer. The initial assessment can help determine the type of cancer a patient has, and subsequent assessments are used to assess the growth or reduction of cancer. Many people undergo surgery to remove their cancer tumours, so a histological image to detect the presence and quantity of cancer cells remaining after the operation is vital to prevent a recurrence. 

 

This postoperative procedure to assess the quantity of remaining cancer cells is called the surgical margin assessment, or SMA for short. It is a histological measurement of the amount of healthy, regular tissue that surrounds a visible tumour. An SMA is often conducted after surgical removal of a tumour to see if the margin was “clean”, where most if not all the cancerous tissue managed to be removed, or “dirty”, where the tumour extends beyond the initial cut margin. 

 

In addition to pre- and post-operative assessments, the future of histology lies in real-time intraoperative imaging. By enabling assessment of histological images during operations, these images can provide guidance in real-time to determine if the surgical margin is good enough to remove most, if not all, of the cancerous tissue. This can significantly improve the surgical margin and reduce the chance of cancer recurrence.

 

What is PhoMedics doing in this space? 

The area of histopathology currently requires lengthy tissue processing, embedding, and staining procedures that can increase the time to diagnosis considerably. Long diagnosis times are not good for patients in an intraoperative scenario. Alao, fast but low and inconsistent results are not favorable for guiding treatments and providing an accurate diagnosis. The intrinsic trade-off between speed and accuracy had limited efforts spent in streamlining the medical workflow. This is where the innovative technology of CHAMP Microscope™ comes in. 

 

The CHAMP Microscope™ is a rapid, label-free, and non-destructive imaging modality that removes the need for the lengthy tissue processing and staining procedures of conventional H&E staining, providing a holistic histopathological imaging solution for medical professionals. CHAMP images, which are grayscale autofluorescence images are transformed into H&E-stained images using the power of a highly-advanced, data-driven deep learning algorithm. The results are so similar, that most have a hard time spotting the difference! Can you differentiate which of the images below is a virtually stained image generated by CHAMP Microscope™ and which one is a result of classic gold-standard H&E staining?

A virtually stained CHAMP image

A gold standard H&E stained image