Pathological anatomy, also called anatomopathology, and frequently, for short, “anapath”, is intended to analyze tissue samples.

This medical specialty studies, more precisely, the lesions of biological tissues, whether living or dead, human or even animals (within the framework of veterinary pathology anatomy). This study of tissues is done with the naked eye, that is to say at the macroscopic level, as well as in microscopy.

It is carried out in the laboratory: the pathologists receive documents to analyze, sent by other specialists. The patient therefore never has direct contact with the pathologist. The primary goal of the discipline is to establish or confirm, or even rectify, a diagnosis evoked by clinical examination, biology data or imaging. To become an anatomo-pathologist, it will be necessary to follow a course of medicine, and to specialize in anatomopathology at the time of the internship.

Pathological anatomy, or anatomopathology, sometimes abbreviated as “anapath”, or even pathology, is a medical specialty. It consists in studying, in the laboratory, lesions of biological tissues, living or dead. It can be human tissue, but also animal tissue (in veterinary pathological anatomy). It is performed by specialist physicians, called anatomo-pathologists or, sometimes, pathologists.

The pathology aims to identify any morphological change in a biological tissue, whether it is related to an inflammatory, degenerative, genetic, tumor, or other pathology. This modification will be evaluated with the naked eye, therefore macroscopically, and microscopically, via histopathology methods.

Unlike the medical biologist, who also works in the laboratory, the pathologist observes biological tissues, while the medical biologist works on fluids, that is to say all biological fluids such as blood, urine, samples from mucous membranes. The biologist will thus evaluate the composition of the blood (hematology), the presence of bacteria or viruses (bacteriology and virology), the chemical constitution of liquids (biochemistry). 

The main goal of anatomo-pathology will be to establish or confirm or even correct a diagnosis. Diagnosis which, initially, will have first been evoked by the clinical examination, the data of the biology and by the imagery.

A patient will never directly consult the pathologist, who works only in the laboratory.

• It is another specialist, consulted by the patient in the context of a pathology, who will decide to have recourse to the pathologist, for the establishment or the confirmation, or even the rectification of a diagnosis evoked by the examination. clinical, biology data, and imaging. 

  In fact, the specialist will send two types of samples to the pathologist, according to their size: biopsies, which are small samples having mainly a diagnostic purpose, and operating parts, of very variable size which can range from a few millimeters. or centimeters to several tens, and can be taken from one or more organs more particularly in the event of tumor pathology.

• In addition, especially in tumor pathology, we can have recourse to the pathologist to study the limits of excision. These cuts constitute the edges of an operative part, they will make it possible to check whether the lesion has been completely removed or not.
• Sometimes a pathological examination is also necessary during surgery. It will make it possible to formally confirm a diagnosis or to analyze the limits of excision, that is to say of the part to be removed. He will guide, more or less differently, the rest of the surgical procedure. This is then an extemporaneous examination: it is carried out by microscopic examination of sections a few microns thick, frozen.
• Pathological anatomy is also performed to study the cells that make up a tissue: this is called pathological cytology, or cytopathology. It aims to analyze cells taken mainly by scraping, such as the cervico-uterine smear for cancer screening, or by puncture of different organs. Limited to relatively accessible lesions, this approach is also a good diagnostic approach. It makes it possible to visualize the cells isolated from the tissue which contains them.
• Finally, anatomopathology can also be used to perform autopsies, in order to understand the medico-surgical causes of death, without prejudging a cause external to the death, accidental or criminal: these remain the role of the medical examiner. But the border between the two sometimes remains thin …

The pathologist, whatever the type of suspected pathology or the type of sample, will have schematically similar management (except for the case of extemporaneous examinations, during surgery). Only the duration of the steps will vary, short for small biopsies, longer for operative parts.

The different steps performed by the pathologist are described below. Beforehand, identification will have been ensured, as well as the fastest possible transport of the sample, preferably in the fresh state. This is easier in hospital structures including a pathological anatomy laboratory; if this is not the case, it will be necessary to add a fixative, mainly formalin (formaldehyde) for transport, which makes it possible to stop the spontaneous degradation of the tissues. Other fixatives, less toxic, also exist, which are used mainly for biopsies or small parts, but are not suitable for larger parts. In addition, the administrative file of the laboratory is drawn up in parallel. The pathologist will then be able to perform his tasks:

• Macroscopic examination. On arrival at the laboratory, the operative part is examined and described as precisely as possible, and the lesions are observed, either fresh or after fixation.
• Fixation with formalin, of variable duration, if the part was sent fresh.
• Long technical step, which is only partially automated, and begins with the sampling. It is materially impossible to examine all of the large surgical specimens under a microscope, and it is not useful. The pathologist therefore carefully samples the lesions observed, their relationship with the neighboring organ (s), the removal of which was necessary surgically, the limits of excision, as well as, for tumor pathology, systematic samples such as lymph nodes that drain the organ. These samples, 2 to 3 square centimeters and approximately 2 to 3 millimeters thick, are placed in perforated “cassettes”.
• The step of inclusion of these cassettes is carried out by an automatic device and includes different baths (alcohol, xylene, paraffin) whose goal is to dehydrate the tissues and replace the water with paraffin, a process that lasts several time.
• Cooling of samples placed on their open cassette, at the exit of the machines.
• A cutting step, thanks to the firmness of the paraffin coating, makes it possible to produce tissue slices, called cuts, of a few microns. The sections will be made using a microtome, before being spread out on glass slides.
• A staining step, by means of new passages in successive baths, will dissolve the paraffin and then specifically stain certain components of cells and tissues, such as nuclei, cytoplasm or interstitial fibers. A new dehydration will be carried out, before laying a thin glass slide on the preparation, using a resin.
• The slides, or sections thus prepared, are then examined under a microscope.
• A detailed report is written, recapitulating the diagnosis, the extent of the lesions, the limits of excision. Currently, this report is largely standardized.

The conservation of the slides being excellent (several decades), it allows long-term archiving.

New complementary techniques have appeared more recently, firstly immunohistochemistry, which makes it possible, thanks to different antibodies, to highlight certain properties and cellular characteristics of a particular type of cells in relation to a disease or a particular tumor type. . More recently, molecular biology has appeared on anatomopathological samples. It is currently necessary and very useful to guide so-called targeted therapies.

The more recent contributions of molecular biology

Indeed, the molecular biology examinations carried out from human tumors now make it possible to optimize the offer of care offered, in the case of cancer patients: thus, the detection of gene mutations, thanks to their amplification. , or that of chromosomal rearrangements, help to target the therapeutic strategy more precisely. This study at the molecular level of tumors can therefore allow what is called personalized medicine, that is to say adapted to each patient, thanks to therapies specifically targeting certain receptors, or other types of molecules. mutations linked to the malignancy process.

In such a context, the discipline of anatomopathology plays a major role because such molecular biology analyzes are possible on dewaxed tissue sections, cells, but also from nucleic acids extracted from tissues included in paraffin (in what mainly concerns DNA, and sometimes RNA) or even frozen tissues (DNA and RNA). The reliability of the result is conditioned by the molecular biology examinations, from which the therapeutic decision will follow: hence the importance here also of the care that the pathologist will have to bring to all the stages of conditioning of a tissue and its tissue. derived products, upon receipt of the sample, and through to the final stages of molecular analysis. Because it will be necessary to be able to analyze a DNA (or an RNA) at the same time well preserved qualitatively, and also present in sufficient quantity. 

These molecular biology analyzes are carried out either in a dedicated anatomo-pathology laboratory or in a biology laboratory: they consist, after extraction of the genetic material on the tissues and cells (DNA and RNA) in carrying out some amplification and possibly sequencing. Such techniques will thus make it possible to detect mutations responsible for cancer, and the clinician can then target them via very specific therapeutic molecules.

To become an anatomopathologist, you will have to follow a medical course, i.e. ten years of medical studies, validating an internship specializing in anatomo-pathology. The pathologist is, therefore, a specialist doctor who will be trained to detect the morphological changes that accompany pathologies, whether it is inflammatory, degenerative, tumor pathology … Once stationed in a laboratory, the pathologist, in fact, will frequently specialize in a few particular pathologies (for example, breast and ovarian cancers) or in certain techniques, such as those, relatively recent, of molecular biology.

The patient will never meet directly with a pathologist, who works in the laboratory. It is always another specialist who will resort to him, depending on the pathology presented by the patient, such as a gastric tumor, breast or ovarian cancer, for example, as well as all kinds of pathologies, inflammatory or degenerative, genetic or tumor, accompanied by morphological changes.

The anatomo-pathologist’s report will often be very technical, by necessity, and sent back to the specialist, who will then be in charge of explaining it clearly to the patient.