Medical Pathology

HOW WOULD YOU DEFINE THE SCIENCE OF PATHOLOGY?

Pathology is the science of diseases. It examines the aetiologies and etiopathogenesis of the diseases, and the changes and functional defects of tissues and organs caused by disease, by employing morphological, immunological and molecular techniques.

What are the targets and duties of the science of pathology?

To guide the clinicians in the treatment protocol they would use by naming the disease (diagnosis) and providing further information on the clinical progression of the disease. Department of Pathology is a part of surgical medicine unit that works in close collaboration with all clinical branches and plays a critical role in diagnosis and determining the treatment strategy of the diseases. It is a disciple that guides the treatment of the patients by detecting many diseases at early stages before they progress to late stage cancers and inform the clinicians accordingly.

What should there be in a pathology laboratory?

There should be pathologists who are expert in different fields of pathology, pathology technicians, and the necessary apparatus, equipments and a microscope.

What methods do you employ in examining a material that arrives into a pathology laboratory?

First of all, small endoscopic biopsies, incisional biopsies etc. should be transported to the pathology laboratory in an air-tight container that contains fixative. Bigger specimens such as organ resections and extremities amputations should be transported immediately to the laboratory wrapped within a clean cloth that does not contain fixative, and these bigger specimens should be opened by employing the proper dissection method and should be incubated in proper containers that enable formalin diffusion into the all tissue layers.

Transportation procedures for cytological materials vary depend on the material. Firstly the specimen is evaluated visually by the clinical pathologist at the macroscopy laboratory by noting the weight, dimensions, colour consistency and any unexpected lesions. Afterwards, depending on the material type and its pathology standardized sampling methods are used. In the hospitals that utilize advanced standards such as ours, fully automated tissue processing equipments are used and the specimens are treated with various chemicals for 14-16 hours to prepare them for the sectioning procedures.

Pathology technicians that are educated to graduate or undergraduate level then take sections of the paraffin-embedded samples by a microtome that can cut the specimens at a 1 thousandth of 1 mm thickness. The sections are then stuck on a microscope slide and are stained by a standard tissue stain called Haematoxylin-Eosin. Following this process tissue samples are ready to be studied under a microscope.

What are the methods used in differential diagnosis in pathology? For what purposes are they used?

Methods used in differential diagnosis:

a) Histochemical stains: It’s an older technique that is cheaper and more basic than Immunohistochemistry (IHC). The purpose here is to show the material build-up in a cell, its basic building blocks or infectious agents (bacteria, fungi). Upon more widespread use of IHC and the broadening of the panel spectrum, the use of histochemical stains has decreased. However, due to its low cost and ease of use some particular stains are still being used routinely in every laboratory.

b) Immunohistochemical stains: It is an immunology-based differential diagnosis method that is based on identifying building blocks inside a cell and the chemical reactions by enzymes that are tagged by special colours. It is used in identifying the tumor type, the tissue the tumor originates from, the normal or extraordinary products produced by it, and therefore it is employed for determining the tumor type and whether tumor specific drugs could be used in the treatment. For example, the presence and the frequency of estrogen (ER) and progesterone (PR) receptors in a breast cancer tumor tissue determines whether receptor blocker treatment (tamoxifen) could be use or not following the surgery. In the same manner, detecting c-erb B2 mutation in the tumor tissue leads to the use of target-specific treatment (Herceptin). Moreover, immunohistochemical methods are used in detecting some mutations that play a role in the aetiology of the tumors (p-53, Rb, EGFR, CD-117). Moreover, it also provides additional information on the clinical progression of the tumors (for example the proliferation rate of the tumor Ki-67).

c) Immunofluorescent microscopy: It is used in diagnosis of some skin, kidney and vascular disease eitologies of which are from immune-based mechanisms. It relies on the principle of identifying the deposited immunecomplexes by fluorescently labelled stains and evaluating the fluorescence by special light filters in dark field. For example, it enables us to see the type of immunecomplexes and where they are deposited in autoimmune diseases such as glomeronephritis, vesiculobullous and vasculitic skin diseases.

d) Electron microscopy: This method is not present in every pathology unit because it is an expensive technique. However, some cell-based build-ups and organelle changes that could not be detected by the abovementioned conventional methods are identified by this method. And especially, the need for this method is high in evaluation of medical kidney biopsies (for showing to which extend the immunecomplexes are deposited in the glomerulus or some extracellular deposits such as amyloid fibrils).

What issues do you pay attention to when preparing and analysing samples? What issues do you pay attention to in reporting the results?

In cases when no definite result can be reached by light microscopy, the abovementioned differential diagnostic techniques are used by starting from the cheapest and the most practical one and working our way up step by step. In reporting the results, the goal is to provide the clinician the most detailed information in the most accurate way regarding the disease.

Is the belief that it takes a long time to get the pathology test results correct?

It takes on average 24 hours for the sections mentioned before to be ready for the evaluation of the clinical pathologist. If the lesion can be identified without differential diagnosis techniques, the results are reported within two days after the light microscopic investigation. Since the pathologist only evaluates the diseased organ without examining the patient, the clinicians should provide a detailed clinical, radiological and laboratory information to the pathologist for the diagnosis. Even though age and sex don’t seem to be important in differential diagnosis, sometimes they play an important role in reaching a diagnosis. Unfortunately, pathologists often have to acquire this information themselves. When advanced differential diagnosis techniques have to be used, reporting of the results could be delayed for a further day or two. The workload, the number of personnel etc. are also important factors for the time it takes to report the results.

In some special occasions (this involves the surgical method used by the surgeon, and the way and the result of the method used), a small sample from the lesion is taken during the surgery and sent immediately to the laboratory while the procedure is still going on. The fresh tissue is touched on a microscope slide by a method called imprinting and the cells that fell are evaluated. Afterwards, the tissue is frozen by special equipment to -20/-25 degrees, sectioned to micron level and evaluated after a fast staining procedure. This method which is called frozen pathology provides diagnosis within a maximum of thirty minutes. Frozen pathology procedure is only used in-surgery and in some special occasions, and it is not a diagnosis method used routinely.

Scientific autopsy

The goal is to observe and identify the morphological changes and symptoms that the disease caused in the organs, to sometimes identify the definite cause of death and to provide information to the clinician on the disease at hand. For this purpose, all three cavities in the human body (skull, chest and abdominal cavities) are opened up and after making the necessary evaluations closed up appropriately.

MEDICAL PATHOLOGY

Cytopathology

  • Gynaecologic cytology
  • PAP Test Screening
  • Non-gynaecologic cytology
  • Effusion cytology
  • Cyst fluids
  • Fine needle aspiration cytology from solid organs
  • Cerebrospinal fluids cytology
  • Urine and bladder wash fluids
  • Cell block preparation
  • Cytochemical staining procedures
  • Immunocytochemical staining procedures

Histopathology

  • Surgical pathology
  • Organ resections
  • Limb amputations
  • Lymph node dissections
  • Incisional biopsies
  • Excisional biopsies
  • Tru- cut needle biopsies
  • Punch biopsies
  • Endoscopic biopsies
  • Histochemical staining procedures
  • Immunohistochemical staining procedures
  • Immunofluorescent staining procedures
  • Frozen sections- Intra operative consultation
  • HPV Genotyping on tissue