Histopathology

Micrograph showing contraction band necrosis, a histopathologic finding of myocardial infarction (heart attack).
Items used for submitting specimens: (Biopsy) wrap, (biopsy) sponge, (tissue processing) cassette and (biopsy) bag.

Histopathology (compound of three Greek words: ἱστός histos "tissue", πάθος pathos "suffering", and -λογία -logia "study of") refers to the microscopic examination of tissue in order to study the manifestations of disease.

- Histopathology

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Pathology

Study of the causes and effects of disease or injury.

A pathologist examines a tissue section for evidence of cancerous cells while a surgeon observes.
The advent of the microscope was one of the major developments in the history of pathology. Here researchers at the Centers for Disease Control in 1978 examine cultures containing Legionella pneumophila, the pathogen responsible for Legionnaire's disease.
A modern pathology lab at the Services Institute of Medical Sciences
A bone marrow smear from a case of erythroleukemia. The large cell in the top center is an abnormal erythroblast: it is multinucleated, with megaloblastoid nuclear chromatin This is diagnostic of erythroleukemia.
A malignant melanoma can often be suspected from sight, but confirmation of the diagnosis or outright removal requires an excisional biopsy.
Pathologist performing a human dissection of the abdominal and thoracic organs in an autopsy room
An instance of diagnosis via histopathology, this high-magnification micrograph of a section of cardiac tissue reveals advanced cardiac amyloidosis. This sample was attained through an autopsy.
This coronal cross-section of a brain reveals a significant arteriovenous malformation that occupies much of the parietal lobe.
This tissue cross-section demonstrates the gross pathology of polycystic kidneys.
Brain biopsy under stereotaxy. A small part of the tumor is taken via a needle with a vacuum system.
Clinical chemistry: an automated blood chemistry analyzer
Many conditions, such as this case of geographic tongue, can be diagnosed partly on gross examination, but may be confirmed with tissue pathology.
An anatomical pathology instructor uses a microscope with multiple eyepieces to instruct students in diagnostic microscopy.
This field post-mortem of a ewe has revealed lesions consistent with acute haemolytic pneumonia, possibly due to Pasteurella haemolytica.
A tobacco plant infected with the tobacco mosaic virus

Further divisions in specialty exist on the basis of the involved sample types (comparing, for example, cytopathology, hematopathology, and histopathology), organs (as in renal pathology), and physiological systems (oral pathology), as well as on the basis of the focus of the examination (as with forensic pathology).

Tissue (biology)

Biological organizational level between cells and a complete organ.

Microscopic view of a histologic specimen of human lung, consisting of various tissues: blood, connective tissue, vascular endothelium and respiratory epithelium, stained with hematoxylin and eosin.
Cross-section of a flax plant stem with several layers of different tissue types:
Cross section of collenchyma cells
Cross section of 2-year-old Tilia americana, highlighting xylem ray shape and orientation
Xavier Bichat (1771–1802)

The study of tissues is known as histology or, in connection with disease, as histopathology.

Cytopathology

Branch of pathology that studies and diagnoses diseases on the cellular level.

A pair of micrographs of a cytopathology specimen showing a 3-dimensional cluster of cancerous cells (serous carcinoma)
Micrograph of a pilocytic astrocytoma, showing characteristic bipolar cells with long pilocytic (hair-like) processes. Smear preparation. H&E stain
A micrograph of an exfoliative cytopathology specimen (Pap test, Pap stain)
Brushes used to collect samples for cytology.

Cytopathology is generally used on samples of free cells or tissue fragments, in contrast to histopathology, which studies whole tissues.

Agar

Jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from ogonori (Gracilaria) and "tengusa" (Gelidiaceae).

Green tea flavored yōkan, a popular Japanese red bean jelly made from agar
A blood agar plate used to culture bacteria and diagnose infection
Ogonori, the most common red algae used to make agar
The structure of an agarose polymer.
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100mm (4") diameter Petri dishes containing agar gel for bacterial culture
Physcomitrella patens plants growing axenically in vitro on agar plates (Petri dish, 9 cm, 3½" diameter).

As a medium to precisely orient the tissue specimen and secure it by agar pre-embedding (especially useful for small endoscopy biopsy specimens) for histopathology processing

Optical microscope

Type of microscope that commonly uses visible light and a system of lenses to generate magnified images of small objects.

Scientists use optical microscopes to examine growing cells
Diagram of a simple microscope
Diagram of a compound microscope
A miniature USB microscope.
The oldest published image known to have been made with a microscope: bees by Francesco Stelluti, 1630
Basic optical transmission microscope elements (1990s)
Two Leica oil immersion microscope objective lenses: 100× (left) and 40× (right)
U.S. CBP Office of Field Operations agent checking the authenticity of a travel document at an international airport using a stereo microscope
A 40x magnification image of cells in a medical smear test taken through an optical microscope using a wet mount technique, placing the specimen on a glass slide and mixing with a salt solution
The diffraction limit set in stone on a monument for Ernst Abbe.
3D dual color super resolution microscopy with Her2 and Her3 in breast cells, standard dyes: Alexa 488, Alexa 568 LIMON
Stimulated emission depletion (STED) microscopy image of actin filaments within a cell.
Bright field illumination, sample contrast comes from absorbance of light in the sample.
Cross-polarized light illumination, sample contrast comes from rotation of polarized light through the sample.
Dark field illumination, sample contrast comes from light scattered by the sample.
Phase contrast illumination, sample contrast comes from interference of different path lengths of light through the sample.

Optical microscopy is used for medical diagnosis, the field being termed histopathology when dealing with tissues, or in smear tests on free cells or tissue fragments.

Visual artifact

Visual artifacts (also artefacts) are anomalies apparent during visual representation as in digital graphics and other forms of imagery, especially photography and microscopy.

A screenshot of a Microsoft Windows XP application displaying a visual artifact with repeated frames.
A retinography. The gray spot in the center is a shadow artifact.
Circular artifacts caused by backscatter from raindrops
Confocal laser scanning fluorescence micrograph of thale cress anther (part of stamen). The picture shows among other things a nice red flowing collar-like structure just below the anther. However, an intact thale cress stamen does not have such collar, this is a fixation artifact: the stamen has been cut below the picture frame, and epidermis (upper layer of cells) of stamen stalk has peeled off, forming a non-characteristic structure. Photo: Heiti Paves from Tallinn University of Technology.
Cellulose contamination, in H&E stain and polarized light
Cardiac muscle (bottom) with contamination from thyroid tissue (center)
Crush artifact from compression by forceps on the tissue sample
Folding artifacts (white arrows) and a crush artifact (black arrow, with cytoplasmic hypereosinophilia and nuclear pleomorphism) from a needle.
Tearing artifacts, such as can be caused by: - Microtomy with a nick or blemish in the knife edge.<ref name="TaqiSami2018">{{cite journal|last1=Taqi|first1=SyedAhmed|last2=Sami|first2=SyedAbdus|last3=Sami|first3=LateefBegum|last4=Zaki|first4=SyedAhmed|title=A review of artifacts in histopathology|journal=Journal of Oral and Maxillofacial Pathology|volume=22|issue=2|year=2018|pages=279|issn=0973-029X|doi=10.4103/jomfp.JOMFP_125_15|pmid=30158787|pmc=6097380}}</ref> - Traction of the sections. - Too much or too little alcohol dehydration. - Sectioning calcified parts, which can be decalcified or removed.
'Formalin pigment artifacts
Air bubble entrapment artifacts
Staining artifacts by residual wax, resulting in pale areas where cellular structures are not discernible.
A separation artifact in top image makes the tumor look incompletely excised, but the next microtomy level (bottom image) shows a surgical margin of connective tissue.
Stacking of cells on top of each other gives a dark look, and in this breast tissue it may mimic microcalcifications.
A hip fracture (black arrow) next to a skin fold (white arrow).
Bed sheets looking like lung opacities on a chest radiograph

A crush artifact is an artificial elongation and distortion seen in histopathology and cytopathology studies, presumably because of iatrogenic compression of tissues.

Perls Prussian blue

Cerebrospinal fluid specimen stained with Perls Prussian blue showing iron containing macrophage (stained blue) surrounded by erythrocytes (stained red)
Section of liver stained with Perls Prussian blue, showing iron accumulations (blue) consistent with homozygous genetic hemochromatosis
Perls Prussian blue stained section of liver biopsy showing hemosiderosis

Perls Prussian blue is a commonly used method in histology, histopathology, and clinical pathology to detect the presence of iron in tissue or cell samples.

Bread loafing

Pictogram of margin controlled histology or CCPDMA
Pictogram of standard bread loafing histology
False negative in standard bread loafing histology

Bread loafing is a common method of processing surgical specimens for histopathology.

Contraction band necrosis

Type of uncontrolled cell death unique to cardiac myocytes and thought to arise in reperfusion from hypercontraction, which results in sarcolemmal rupture.

High magnification micrograph showing contraction band necrosis and karyolysis. H&E stain.
Contraction band necrosis. H&E stain.
Contraction band necrosis. PTAH.

The name of the histopathologic finding comes from the appearance under the microscope; contraction bands are thick intensely eosinophilic staining bands (typically 4-5 micrometres wide) that span the short axis of the myocyte.

Avian adenovirus

Aviadenoviruses are adenoviruses that affect birds—particularly chickens, ducks, geese, turkeys and pheasants.

Adenovirus D26 structural model at atomic resolution

Diagnosis of aviadenovirus is by histopathology, electron microscopy, viral isolation, ELISA and PCR.