Pathology: Cytology/Histology

Thanks to modern high-quality veterinary care, pets are becoming steadily older and the relative prevalence of cancer is increasing. Pets are part of the family and consequently owners expect the same level of medical care for their animal as for themselves and their children.  The services of Histopathological studies are offered by Averroes Laboratories (ARL) on demand. 

PARR: a PCR for the unravelling of canine lymphoproliferative disorders

Lymphoproliferative disorders represent a significant clinical problem in dogs. It is crucial to differentiate neoplastic lymphoid disease – i.e. lymphomas and leukaemias – from reactive, hyperplastic lymphoid conditions. Nevertheless, the unravelling of nodal or extranodal lymphoproliferative conditions frequently represents a diagnostic challenge for veterinary pathologists. PARR test will supply additional information about the clonal, i.e. neoplastic nature of lymphoid cells, or the polyclonal, i.e. reactive nature of lesional lymphoid cells. While the combination of histopathology and immunohistochemistry is a powerful tool to accurately assess the neoplastic or reactive nature of a lymphoproliferative condition in significant percentage of such cases, the essence of lymphoid neoplasia – i.e. the clonal expansion of neoplastic lymphoid cells – cannot be proved by this microscopic approach. 

Basics of PARR

The canine PARR test is based on the sequences of all loci involved in canine lymphocyte antigen receptor rearrangements. The PARR has been validated in a very large range of canine lymphoproliferative lesions, including all subtypes of canine lymphomas, according to the current WHO classification. So the test has been validated in the various types of large cell lymphomas, small cell lymphomas and indolent lymphomas. Also rare subtypes like angiocentric lymphomas were included in the test panel. Furthermore, the various intestinal and cutaneous lymphomas were included, as well as  the recently characterised hepatosplenic canine lymphoma. 

Additional information

Both paraffin-embedded, formalin-fixed tissue and smears are suited for analysis by PARR. In the case of smears as DNA source for the PARR, we prefer stained smears, as a visual inspection of the smear is necessary to make an assessment of the amount of DNA that can be isolated from the smears. Preferably submit several stained smears. The staining procedures used in cytology do not interfere in a negative way. For formalin-fixed tissues, please submit the wax block, which will be returned once the results of the PARR test have become available. If it is not possible to submit the wax block, please submit three 10µm paraffin sections in an Eppendorf tube and a 4µm HE-stained mounted section of the wax block for a microscopic inspection of the tissue. We report on  PARR results in both the T-cell and B-cell populations. The results are reported in 5 to 10 working days (depending on the day of arrival of the tissue).