Fancy an introduction to lymph node cytology and discussion of a few clinical cases? Join me online on the 18th of August for this free cytology webinar offered by Heska. I can’t wait to connect with you all. Registration at the link below.
This program has been approved for 1 hour of continuing education credit in jurisdictions which recognize RACE approval.
Melanoma is considered on cytology the great pretender. In fact, neoplastic cells may vary in shape ranging from round to polygonal and spindle.
This can make the diagnosis very difficult, in particular in amelanotic forms, where melanin granules are either absent or present in very low numbers. In those cases, a definitive diagnosis may require further testing and in particular immunocytochemical stains (ICC).
On a publication from 2015 on 38 cases of canine oral neoplasms, the combination of cytology and ICC (cytokeratin, vimentin, and Melan A) showed a very high sensitivity and specificity for the presurgical diagnosis of amelanotic melanoma. Early identification of this tumour is considered crucial from a clinical point of view, as ability to metastasise to local lymph nodes and other organs is significantly higher than other oral tumours. Treatment involves local tumour control through surgery and/or radiation therapy, as well as systemic treatment.
In many cases, it is possible to identify the animal species by looking at the peripheral blood under the microscope as there are often selected species-specific features. For example, guinea pigs are characterised by the presence of heterophils and Foa-Kurloff cells.
Peripheral blood, guinea pig, 100x
Heterophils are the counterpart of neutrophils and are seen in selected small mammals, birds, amphibs and reptiles. They are characterised by round to rice shaped brick red granules seen in variable numbers within the cytoplasm.
Foa-Kurloff cells are another leukocyte type that is unique to guinea pigs. They are specialized mononuclear cells that contain an intracytoplasmic inclusion body of mucopolysaccharide, which appear variably pink and granular. Although Foa-Kurloff cells can be present in the blood of both males and females, they are most commonly observed in blood smears from pregnant guinea pigs. These cells may be more prominent during pregnancy because they shift from the lungs and spleen to the thymus and placenta under oestrogen stimulation. Foa-Kurloff cells possibly function as natural killer cells.
Spontaneous tumour regression is defined as spontaneous remission or disappearance of a tumour in the absence of any treatment. This can also be observed in animals and in particular in two conditions: cutaneous histiocytoma and transmissible venereal tumour (TVT).
Figure 1. Regressing cutaneous histiocytoma, dog, Wright Giemsa, 50x.
Cutaneous histiocytoma is a common benign canine skin tumour. Spontaneous regression within a few months is a common finding and is accompanied by a progressive lymphocytic infiltrate, which eventually spreads throughout the lesion. The heavy lymphocytic infiltrate that occurs in late-stage regression of histiocytomas can be mistaken for non-epitheliotropic T-cell lymphoma. Definitive diagnosis is preferably reached by histopathology. Flow cytometry and PARR testing are other considerations; however, their results can be misleading as clonal expansion of CD8+ lymphocytes has been described in regressing histiocytoma and may mimic lymphoma.
Transmissible venereal tumour is another neoplasm of histiocytic origin described in the canine species and associated with spontaneous regression.
Figure 2. Transmissible venereal tumour, dog, Wright Giemsa, 50x.
In both conditions, the mechanism of spontaneous regression is not fully understood but activation of immune system is likely to play a key role.
Based on a recent cytology grading system proposed by Camus and colleagues, canine cutaneous mast cell tumours can be graded cytologically and being classified as low or high grade, based on the presence / absence of specific morphological features. The algorithm below taken from the original publication shows the criteria used for grading purposes.
Cutaneous mass, Dog, High grade mast cell tumour, Wright Giemsa, 50x
The cytologic algorithm that most closely correlated with histologic grade classified a MCT as high grade if it is (1) poorly granular or (2) has at least 2 of the following 4 features: presence of any mitotic figures, anisokaryosis, binucleation or multinucleation, or nuclear pleomorphism. This system showed a good correlation with clinical behaviour and cytologic high grade tumours were associated with significantly decreased probability of survival. However, both false positive and false negative results occurred, suggesting histopathology grading is still recommended after surgical removal of the mass. Histopathology will also provide important further information, such as surgical margins. In selected cases, from the histology sections it is also possible evaluating proliferative markers (e.g. Ki67) which can provide additional prognostic information.
THE NEW WEBSITE IS ONLINE!
The new website is finally online!
Have a browse, you will notice a new look, brand new sections and most importantly an updated cytology/haematology atlas with hundreds of pictures.
Spread the word and have fun!
ESAVS ONLINE COURSE - CYTOLOGY II
This cytology course will take place online from 14th to 18th of March 2022. It will focus on areas of cytopathology that are clinically relevant but tend to be examined by experienced personnel. The topics covered include cytology of internal organs (e.g. thoracic organs, liver, spleen, pancreas, adrenal glands, gastrointestinal tract, uro-genital tract), cytology of fluids (e.g. nasal flush, TW, BAL, synovial fluids, CSF), and other districts (e.g. musculoskeletal system, eyes, histiocytic disorders). There will also be a small session on histopathology covering all the information a veterinarian should know before collecting and submitting a histopathological sample for analysis to an external laboratory. Correlation cytopathology-histopathology will also be discussed.
Similarly to CYTOLOGY 1, every day the participants will be presented with digital cytology cases to solve in order to put in practice what they learned during the course. Digital cytology will give you the same experience as being in front of the microscope and is the best way to learn cytology from home.
Fluid Cytology for General Practice Course
Is learning cytology one of your 2022 resolutions? Checkour online tutored cytology course starting on January 10th. Three weeks together to learn everything about cytology of fluids in dogs and cats (cavitary effusions, synovial fluids, TW, BAL, CSF, urine).
On demand webinars, study material, digital cytology cases and a forum to interact with me at any time.
Look at the course program at the link below.
See U there.
Free webinars coming soon
Do not miss this series of talks focused on CANINE MAST CELL TUMOURS that we have planned for October in collaboration with Virbac and BattLab/LABOKLIN. It will be the chance to go through this very common tumour in dogs from different perspectives, from oncology, to cytology, histopathology and markers of proliferation.
To register to these free webinars, you can follow the links below.