The pathology department consists of a team of Board-certified and experienced anatomic and clinical pathologists and technicians committed to providing a comprehensive diagnostic biopsy, cytology and post mortem service.


Jennifer Stewart BS, DVM, DipACVP (Anatomic & Clinical), MRCVS , Anatomical and Clinical Pathologist

Hannah Wong MA VetMB PhD DipACVP MRCVS, Anatomical Veterinary Pathologist

Bernardo Saucedo Garnica DVM, Msc, PhD, DiplECVP, MRCVS, Anatomical Veterinary Pathologist


The Animal Health Trust (AHT) offers a biopsy (histology) service which includes examination of both surgical biopsies and post mortem samples, delivered by our experienced and approachable team of pathologists.

Our pathologists are all on-site and are always willing to discuss cases and offer advice on related matters such as appropriate sampling techniques. In difficult or challenging cases the final histology report will often reflect a ‘consensus opinion’, reached after examination by more than one pathologist.

We have a turn-around time of approximately 24-36 hours from receipt. In exceptional cases, such as large samples (that may need additional fixation prior to processing) and samples that require decalcification (including toes and bone biopsies) the turnaround time may be longer. We endeavour to keep you, the client, informed in all cases in which delay are expected.

In urgent cases suitable samples can also be reported on the day of receipt for a small additional fee (contact us and ask to speak to our histology laboratory for further details).

In addition to routine H&E staining normally used for histopathology, we also use a wide variety of special stains (including stains for copper accumulation in canine livers) to improve the accuracy of our diagnoses. These stains are done at the pathologists’ discretion, usually at no extra cost. However, if stains, such as the silver stains for fungi, is required (or requested by you) an additional charge may be incurred. We will NOT add any additional cost without prior consultation.

Biopsy samples should be submitted in 10% neutral buffered formalin in a non-glass leak-proof container. The ideal ratio between tissue and formalin should be 10:1, to insure adequate fixation. Especially in larger samples such as samples taken at post mortem/necropsy the thickness should ideally not exceed 10mm. Large samples should be partially incised through the superficial aspect to minimize distortion during fixation.


Immunohistochemistry (IHC) is playing an increasingly important role in modern veterinary pathology. It is a valuable tool in both diagnosis and research of infectious and neoplastic diseases in animals. A key benefit, IHC is performed on the same tissue samples on which histological evaluation is made; therefore IHC does not require additional sample collection or invasive procedures. This also allows for direct visual comparison of the targeted lesion with the tested antibody.

Immunohistochemistry is used to identify specific proteins within cells, tissues or organisms via antibodies which bind to the protein in question. This binding is followed by a chemical reaction which results in production of a colour which can be seen under the microscope.

Immunohistochemistry at the Animal Health Trust (AHT) is performed on a state-of-the-art automated system designed specifically for this procedure, allowing processing of large volumes of cases and ensuring reproducibility, accuracy and a fast turn-around time. ‘Manual,’ or bench-side, IHC is also performed for novel research antibodies. All IHC protocols at the AHT are standardised and optimised and quality control is strictly monitored with every test performed, including known positive controls.

Here at the AHT, focus is primarily on diagnostic and/or prognostic markers for neoplastic diseases, principally in dogs, cats, and horses. This may include classification of ‘undifferentiated’ tumours and/or lymphomas, evaluation of metastatic tumours for site of origin, and identification of micro-metastatic disease in sentinel lymph node biopsies taken from cancer patients. This technique plays an important role in assessing prognosis in some cancer patients (e.g. via proliferative proteins, such as Ki67 in mast cell tumours) and directing treatment protocols. Identification of infectious agents (e.g. Equine Herpesvirus) aids in treatment and preventing epidemics.

For enquiries about our immunohistochemistry services, please contact  or call 01638 552993.

New immunohistochemical tests available

The variable behaviour of mast cell tumours and melanomas in dogs makes it difficult for many veterinary practitioners to offer their clients an accurate prognosis and the best treatment.

We are excited to announce that we have implemented immunohistochemical tests, many pioneered at the Trust, for assessing tumour proliferation, which is one of the most important predictors of the risk of metastases and recurrence.

The Ki-67 proliferative marker, usually investigated in canine mast cell tumours of the skin, can now also be assessed at the AHT in mast cell tumours arising in the subcutis and in melanomas arising in the oral cavity, lips, skin, and digits.

In addition, we also offer the evaluation of a newly discovered proliferative marker (Minichromosome Maintenance Protein -7) for canine cutaneous mast cell tumours which has been revealed to be significantly associated with patients’ survival.

For more information, please contact

Post Mortems

The Allen Centre at the Animal Health Trust (AHT) is a state-of-the-art post mortem facility completed in 2001 and immediately used as the diagnostic centre of the Foot-and-Mouth outbreak due to its containment features. The laboratory is outfitted for companion animal, equine and small exotic animal post mortems.

What is a post mortem?

Post mortem examinations (necropsies) are performed on deceased animals to determine the probable cause(s) of death or to collect specimens for additional testing, which may aide in selecting the appropriate treatment for other animals in a stud, house, kennel or litter of animals. Necropsies may also be performed on the basis of legal or disease investigation needs.

What are the benefits of a post mortem?

Post mortems can benefit:

The owner: Offering closure during this traumatic time by confirming a clinical diagnosis or the severity of disease, or by identifying the cause of sudden death.

The owner and attending vet: Providing information on probable cause(s) of death, which may be beneficial in the selection of appropriate treatment for other animals in stud, house, kennel or litter.

Veterinary knowledge: Through improvement of clinical understanding of disease processes, education of clinicians and, if appropriate, furthering veterinary knowledge through research.

The process

Necropsy prices include the post mortem examination with a macroscopic (‘gross’) report, and all, if any, required in-house histology to evaluate for a probable cause of death. Samples may be taken, with consent, for additional recommended testing, such as bacterial culture and viral isolation. In some instances additional testing may be outsourced to speciality labs (e.g. toxicology) in which instances charges for these tests are at the rate of the subcontracting lab.

Important points

  • Post Mortems are performed at the Allen Centre on various species, with the following exceptions: Birds / Reptiles / Cattle / Pigs / Primates / Marine Life / and animals that have recently had chemotherapy.
  • The Animal Health Trust is a referral hospital, and as such all requests must be made through a referring vet prior to arrival, and requests cannot be accepted from the owner themselves. Note: Please ensure the owner is fully aware that the AHT will only converse with the referring veterinary practitioner on any matters pertaining to the post mortem.
  • Ideally, patients should be kept cooled and sent to the AHT as soon as possible to preserve diagnostic integrity.  If a notable delay is expected freezing may be recommended. NB Freezing neurology cases (Brain / spinal cord) is not advisable, and consultation with a pathologist is encouraged if such a case is likely to be delayed.
  • An appropriate courier service may be utilised for transportation of suitably contained submissions. The Allen Centre hours of operation are Monday – Friday 8am – 5pm. A weekend on-call post mortem service is provided for equine submissions under the auspices of the HBLB, ROA, and TBA; please contact us on the normal telephone number above to make arrangements with the on-call pathologist.
  • Due to legal restrictions remains cannot be returned to the owner prior to cremation. Group cremation is included in the cost, however private cremation can be requested (at extra cost), and the ashes returned. Relevant costs can be found in our price list, available below
  • As part of our mandate we not only treat diseases, but strive to prevent and understand them, as such donations of beloved pets for the purpose of furthering knowledge are often made and interested parties may liaise with the appropriate department(s) if they wish to donate.
  • If a body is donated solely for research purposes, there is no charge, provided the animal goes for mass cremation.  Private cremations will be charged. In all cases, please consult with our Pathology Department prior to submission.
  • Submission forms for post mortems can be downloaded below.

Equine herpesvirus (EHV) diagnosis

Diagnosis of EHV can only be carried out in the laboratory. The Animal Health Trust is a World Organisation of Animal Health (OIE) reference laboratory for EHV-1.

EHV clearance for equine abortion and neonatal death

We recommend that EHV clearance for animal movement on breeding farms following an abortion should be based on a three-stage testing procedure to avoid the risk of false positive or false negative results. This includes a gross post mortem examination with histological examination of fixed fetal and placental tissue sections and the EHV DNA PCR test.

Clearance tests can be carried out on selected tissues sent to the Animal Health Trust (AHT) following gross post mortem examination elsewhere (Option 1) or as part of a complete post mortem investigation carried out by us (Option 2).

Option 1: Postal Samples

Following a preliminary gross post mortem examination performed by the attending veterinary surgeon, appropriate tissues for herpesvirus diagnosis or clearance are: fetal liver, lung, spleen, adrenal gland and thymus. Pooled fresh tissue preferably in transport medium (or otherwise in a labelled sterile container) should be submitted for PCR and tissues fixed in 10% neutral buffered formalin (NBF) should be submitted for histopathological examinations. A second paired set of samples labelled from the chorion (cervical star, body and both horns) should also be submitted in transport medium for PCR and in NBF for histopathological examinations.

The cost for the combined PCR and histological testing is £80.00* and the usual turnaround time for both tests is up to 48 hours for samples received Monday to Thursday, and up to 72 hours for samples received at other times. Where the two tests give discrepant results (or only fixed tissue is received) immunohistochemical stain will be performed within the total £80 charge, results take up to one week.

Option 2: Post Mortem Examination Performed at AHT

The post mortem examination involves consideration of Equine Herpesvirus status, as well as other potential causes of abortion or neonatal death. The placenta should always be submitted with the fetus where possible. The cost of the post mortem examination is £200.00* including laboratory and disposal charges. Turnaround time is as in Option 1 above.

All EHV-1 diagnoses are copied to the AHT epidemiology team, who are able to offer advice on further testing, isolation and movement of horses.

Further information can be found in the Horserace Betting Levy Board Code of Practice on Equine HerpesVirus-1, which is available here

Equine abortion and neonatal foal death

Prompt diagnosis of any abortion or neonatal foal death is important in safeguarding the present and future reproductive health of the individual mare and, in the case of infectious abortions (such as EHV-1 or ‘viral abortion’) in reducing risk of further abortions or foal losses by in-contact mares. Because the major source of infection in cases of viral abortion is the aborted fetus, and to a lesser extent the fetal membranes and fluids, the aborting mare must be isolated from any other stock especially mares in late pregnancy until a diagnosis has been made. Meanwhile, movement of horses on and off the premises should be stopped.

Diagnosis of the cause of abortion is made by examination of the fetus and membranes, which should be sent to a veterinary pathology laboratory experienced in equine abortion and neonatal death investigations, carefully contained in a leak-proof bag, with the help and advice of the attending veterinary surgeon. The mare should be examined by a veterinary surgeon to check for any complications related to the abortion, such as retained placenta.

If it is not possible to send the whole fetus with placenta, or foal to the laboratory, samples of the following tissues should be collected to achieve rapid herpesvirus abortion clearance: pooled liver, lung, spleen, adrenal gland and thymus with placenta (cervical star, body and both horns in a separate tube.

Using microscopic examination of tissues collected from the fetus and placenta, in combination with the PCR test, which is sensitive enough to detect even minute quantities of viral DNA, it is usually possible to achieve a diagnosis of herpesvirus abortion within 48 to 72 hours.

If herpesvirus infection is confirmed, isolation, movement restrictions and strict hygiene procedures should be followed. These procedures are detailed in the Horserace Betting Levy Board (HBLB) Code of Practice for Equine herpesvirus (EHV). Copies of the code may be requested from the HBLB (telephone 020 7333 0043), and are available here.

The Animal Health Trust operates a seven day-a-week abortion screening service using the procedures outlined above, and can be contacted by the stud veterinary surgeon in the event of an abortion.