Journal of Clinical & Experimental Pathology
Open Access

Histopathology is the microscopic anatomy of tissues, which is used largely to diagnose illnesses. This field of pathology examines tissues under a microscope to detect anomalies which indicate diseases like cancer, inflammation, and infections. Histopathology, which examines tissue samples in detail, is important in diagnosing, understanding, and treating a variety of medical disorders. Histopathology shares many similarities with clinical and experimental pathology. Clinical pathology diagnoses diseases through laboratory study of biological fluids, tissues, and cells, whereas experimental pathology studies disease causes through research and laboratory experiments. Both healthcare providers depend on histopathological techniques to better understand the basic causes of disease, provide new diagnostic tools, and test treatments. The term histopathology comes from the Greek words "histo" (tissue), "pathos" (disease), and "logos" (research). It refers to the microscopic inspection of tissue to identify disease symptoms. Histopathologists are specifically trained clinicians who use various staining techniques to identify disease-related alterations in cells from biopsies and other tissue samples. Tissue collection, typically through biopsy, surgery, or autopsy, is the first step in histopathological evaluation. Chemicals such as formaldehyde are used to preserve the tissue and keep it stable for microscopic examination. The fixed tissue is covered in paraffin wax, which offers support for breaking tiny sections for microscopic analysis.

The tissue sections are treated with chemicals such as Hematoxylin and Eosin (H&E), which helps in the differentiation of various cellular components and structures. Specialized stains, such as immunohistochemical stains, can be used to detect specific proteins or cellular markers. After the tissue is produced, pathologists examine the slides with blood under a microscope. They check for cellular alterations that may indicate a disease. Pathologists examine cancer cells for atypical growth patterns, irregular nuclei, increased mitotic activity, and other signs of malignancy. The pathologist's results are then put into a report and given to the treating physician, who utilizes it to guide the patient's care. Many diseases, especially cancer, depend mainly on histopathology for diagnosis. However, its utility goes beyond oncology. It is used to study infectious diseases, inflammatory problems, autoimmune disorders, and neurodegenerative diseases. In oncology, histopathology is used to diagnose and stage cancer. The microscopic examination of tissue identifies malignant cells and helps in the determination of cancer type and grade. This information is essential in determining if surgery, chemotherapy, or radiation therapy is the best course of action. Histopathological examination is used to identify infections, especially when pathogens like bacteria, fungus, or parasites are difficult to detect in cultures or serological testing. Special stains (e.g., Gram stain, acid-fast stain) and molecular techniques (e.g., in-situ hybridization) can detect the presence of infections.

Chronic inflammation, as seen in Crohn's disease, ulcerative colitis, and rheumatoid arthritis, has the potential to cause serious tissue damage. Histopathology shows the amount of the inflammation, tissue destruction, and the existence of granulomas or other distinguishing signs which help in diagnosis. Following organ transplantation, histopathology is essential for monitoring rejection or infection in the transplanted organ. Histopathology is extremely useful in medical research, particularly in drug development and disease processes. Animal models are frequently subjected to histopathological investigation in order to assess medication efficacy or disease development. Histopathology has changed throughout time to accept new technologies, which improve diagnostic accuracy and provide deeper insights into diseases. IHC is a technique that uses antibodies to detect certain proteins in tissue sections. It is commonly used in cancer diagnosis to identify tumor markers that can influence treatment decisions, such as hormone receptors in breast cancer (e.g., estrogen receptor, progesterone receptor) and HER2 status. It can also help to better classify various types of cancers.

Electron Microscopy (EM) has far greater resolution than light microscopy, allowing for detailed analysis of cellular organelles and structures. It is especially beneficial for detecting some kidney ailments, neuromuscular abnormalities, and viral infections. In recent years, digital pathology, which involves scanning histopathological slides to create high-resolution digital images, has grown in popularity. These photos can be evaluated with AI algorithms to help with diagnosis, provide quantitative data, and reduce diagnostic errors. In cancer diagnoses, histology and clinical pathology collaborate. A biopsy may be performed, and the histopathologies will inspect the tissue for malignant alterations. Meanwhile, clinical pathologists may examine blood tests, tumor markers, and molecular diagnostics to get a full picture of the patient's health.

Histopathology is a fundamental aspect of modern medicine, providing critical insights into disease diagnosis and treatment. Its application extends to both clinical and experimental pathology, overcoming the difference between the laboratory and the clinic. As technologies advance and new diagnostic procedures develop, histopathology is going to have an increasingly important role in improving patient outcomes, advancing medical research, and contributing to a better knowledge of disease causes.