Abnormal Sysmex XT-2000iV DIFF scattergram in a cat with a prominent mastocytemia

A 2-year-old neutered male domestic shorthair cat was presented to the emergency service of the National Veterinary School of Toulouse (France) for acute vomiting and diarrhea with lethargy, inappetence, and adypsia for the past 48 hours. Complete blood counts were performed with the ProCyte DX at the emergency department and with the Sysmex XT-2000iV at the laboratory 2 weeks later. The scattergrams from the two analyzers revealed similar unusual and abnormal dot plots. The Sysmex XT-2000iV DIFF scattergram also showed no clear separation between different leukocyte populations. The eosinophil cluster was in an abnormal location compared with that of the "typical" location in a normal cat. A blood smear evaluation revealed the presence of numerous mast cells. Thus, we hypothesized that the Sysmex XT-2000iV had detected the mast cell population, and this led to errors in the differential counts. To explore this hypothesis, we manually gated on the DIFF scattergram and performed a manual differential on the blood smear. With this new gating strategy, the Sysmex XT-2000iV and manual differentials were similar. Thus, in the case of systemic mastocytosis, mast cells can be located between the lymphocyte, monocyte, and eosinophil clusters on scattergrams.

The feline blood film

Practical relevance: Many veterinary practices have invested in quality automated hematology instruments for use in-house. However, regardless of their specific choice of analyzer, there are important hematology findings that can only be determined by microscopic examination of stained blood films. For this reason, and also for the purpose of quality control for the analyzer, a quick blood film review should be performed alongside every automated complete blood count. Even those practices that submit their blood samples to outside diagnostic laboratories for evaluation, still require the capability to examine stained blood films in emergency situations. Series outline: This is the second of a two-part article series that aims to familiarize the practitioner with normal findings on feline blood films, with a particular focus on unique features in the cat, as well as to assist with interpretation of common abnormalities. Part 2 focuses on the morphology of feline leukocytes and platelets in health and disease. Evidence base: The information and guidance offered is based on the published literature and the author's own extensive clinical pathology research.

Mastocytemia associated with a visceral mast cell tumor in a Sumatran tiger (Panthera tigris)

A 6-yr-old male Sumatran tiger (Panthera tigris) with no significant past clinical history was anesthetized for clinical examination after 5 days of lethargy. Clinically, the animal presented with anorexia, pale mucous membranes, and icterus. Hematologic results indicated moderate anemia and severe thrombocytopenia and showed a circulating population of atypical mast cells. The tiger died during anesthesia. On postmortem examination, abdominal hemorrhage associated with marked diffuse hepato-splenomegaly and mesenteric, hepatic, and splenic lymph node hypertrophy were observed. A visceral mast cell tumor was confirmed by histologic examination and toluidine blue staining, with splenic, hepatic, lymphoid, renal, and pulmonary infiltration. Hematologic, postmortem, and histologic findings were consistent with mastocytemia associated with the splenic form of mast cell tumor described in domestic cats.

Mast cell tumors in cats: clinical update and possible new treatment avenues

PRACTICAL RELEVANCE

Feline mast cell tumors (MCTs) are frequently encountered in general practice. MCTs are the most common splenic tumor, second most common skin tumor and third most common intestinal tumor in cats. Treatment and prognosis can vary dramatically with location and histologic classification.

CLINICAL CHALLENGES

While a cytologic or histologic diagnosis is often easy to obtain, the various histologic classifications, lack of a relevant grading scheme, and disparity in behavior depending on anatomic location make prognostication for cases of feline MCTs confusing. This is quite different from canine MCTs, where there is an established grading system which correlates clinically with prognosis and an accepted standard of care.

AUDIENCE

Due to its prevalence, general practitioners encounter MCTs regularly. In many instances, referral for diagnosis and treatment is not necessary.

EVIDENCE BASE

Historically, there has been limited clinical evidence upon which to determine optimal treatment of MCTs in cats. Most recommendations are based on limited case reports or retrospective studies. With the recent introduction of receptor tyrosine kinase inhibitors to the veterinary market, there has been new research on the use of these drugs in cats, and new treatment options are on the horizon.

Mastocytaemia in cats: prevalence, detection and quantification methods, haematological associations and potential implications in 30 cats with mast cell tumours

The significance of mastocytaemia in cats is different from that in dogs because it appears exclusively associated with mast cell neoplasia. The prevalence of mastocytaemia was 0.05% of all feline submissions to a private laboratory and 43% in cats with mast cell neoplasia. None of 30 healthy cats had mastocytaemia. There was no sex bias or significant age difference between mastocytaemic and non-mastocytaemic cats with mast cell tumours (MCT). Buffy coat (BC) examination was the best screening method for detection of mastocytaemia but direct blood film examination was more accurate for quantifying degree of mastocytaemia. BC examination should be performed in all cases of suspected/known mast cell neoplasia as mastocytaemia was missed on nearly 30% of occasions when direct film examination only was used. Mastocytaemia was associated with decreased haematocrit (HCT) but not with other haematological parameters. Mastocytaemic cats can survive significant lengths of time (up to 27 months) even when splenectomy is not performed.