#cell pathology

[biomedicool]

Liver Disease Histology

Most cases can be diagnosed on tissue sections utilising Haematoxylin & Eosin. The main feature to identify is resemblance to normal liver – i.e. plate like growth and cytology.

Most staining methods are modified trichromes: 

Shikata orcein - binds to elastic fibres, Hep B surface antigen, Cu-binding proteins 

Phloxine tartrazine - Stains viral inclusion bodies (below)

Reticulin 

the reticulin network is particularly rich in the liver 

following hepatocyte necrosis, surrounding reticulin fibres collapse into the space left behind 

areas of reticulin crowding indicate hepatocyte loss 

also shows areas of regeneration 

now frequently used e.g. for hepatatis B: utilising antibodies specific to either the core antigen (HBc)or the surface antigen (HBs) 

Reticulin stain highlighting the reticulin pattern in acute hepatic necrosis. The hepatocyte cords are focally expanded (H), and a band‐like area of reticulin collapse (arrows) near the central vein (CV) highlights the necrosis (magnification ×200). (x)

[biomedicool]

Oncogenes

An oncogene is a gene which, in the right circumstances, can transform a cell into a tumour cell. 

Exogenous - originating outside the body, include viral oncogenes which may be introduced into cells by tumour viruses Endogenous  - genes that are normally present in the cell but have been altered to produce the oncogene - this alteration can be called activating.

Proto-oncogenes - “dominant” (only one allele necessary),  genes that normally help cells grow. When a proto-oncogene mutates, or there are too many copies of it, it becomes permanently activated and the cell grows out of control --> tumour.

Tumour suppressor genes - “recessive”,  normal genes that slow down cell division, repair DNA mistakes, or tell cells when to die (apoptosis). These are like the brakes of a car; when inactivated, cells grow out of control --> tumour. 

The functions of oncogenes can be altered by:

point mutations 

amplifications

gene rearrangements/translocations

deletions of part or all of the chromosome

altered expression*

*Altered expression/epigenetics 

Occurs without any mutational event - no change in the nucleotide sequence, therefore would not be picked up in DNA sequences. E.g. changes in the methylation patterns of the promoter region of the gene leads to an altered expression in the transcription of the mRNA and its translation.