Paraneoplastic hypereosinophilic syndrome in a cat with lymphocytic intestinal lymphoma (single case report, FeLV-negative)
Brazilian journal of veterinary medicine · 2026
In plain language
This is a report on one cat: a 13-year-old neutered male Persian with lymphoma in the intestine. The cat had an extremely high count of a type of white blood cell called eosinophils. The cat was reported as negative for FIV and FeLV, so this case says nothing about cats with FeLV. The authors themselves note that why this happens in cats is still poorly understood.
Scientific detail
This is a single, uncontrolled clinical case of a 13-year-old neutered male Persian cat reported as negative for FIV and FeLV. The method of FIV/FeLV testing is not reported, so the result cannot be used to judge the sensitivity or scope of the testing.
Histopathology of duodenal, jejunal and mesenteric lymph node biopsies confirmed feline lymphocytic alimentary lymphoma. Immunophenotyping is not reported, so T-cell lineage is not established in this individual.
Repeat hematology documented 81,500 leukocytes/µL and 69,000 eosinophils/µL, with no immature eosinophils in peripheral blood. Mature morphology alone does not establish whether the eosinophilia is reactive or clonal. The bone marrow profile was consistent with reactive eosinophilic hyperplasia, but cytomorphology alone could not exclude chronic eosinophilic leukemia; the authors reiterate this limitation in the discussion. Allergic and parasitic causes are described as excluded, but the detailed exclusion testing is not reported.
No cytokine measurements or molecular clonality testing were reported. Cytokine-mediated mechanisms are presented as proposals extrapolated from feline, canine and human cases; cytokine production by this cat's lymphoma was not demonstrated. The case provides differential-diagnosis context between lymphoma and eosinophilic leukemia in cats, but does not establish FeLV-associated oncogenesis, a viral mechanism, or applicability to FeLV-positive cats.
What we know
In this one cat, intestinal lymphocytic lymphoma was confirmed by biopsy and extreme peripheral eosinophilia was documented, with a bone marrow profile consistent with reactive eosinophilic hyperplasia. It is a single case, and the cat was reported as FeLV-negative.
What we don't know
The exact pathophysiology of lymphoma-associated hypereosinophilia in cats remains poorly understood. In this case, chronic eosinophilic leukemia cannot be excluded by cytomorphology alone, and immunophenotype, cytokines, molecular clonality and the FIV/FeLV testing method are not reported. This case provides no evidence in FeLV-positive cats.
Evidence
EvidenceLevel C — Preliminary evidenceConfidence 100/100
The reported lymphoma case involved a 13-year-old neutered male Persian cat described as negative for FIV and FeLV.
Excerpt verified in the source — verbatim, in the source's own language“A 13-year-old neutered male Persian cat, negative for FIV and FeLV, was presented with a four-month history of frequent vomiting.”
This establishes the reported patient characteristics and retroviral status, not the sensitivity or scope of retroviral testing. The testing method is not reported, and this is not evidence from an FeLV-positive lymphoma case.
EvidenceLevel C — Preliminary evidenceConfidence 100/100
Histopathological examination of duodenal, jejunal, and mesenteric lymph node biopsies confirmed feline lymphocytic alimentary lymphoma.
Excerpt verified in the source — verbatim, in the source's own language“After the results, it was decided to perform a biopsy of the duodenum, jejunum, and mesenteric lymph node, in which the histopathological examination confirmed the diagnosis of feline lymphocytic alimentary lymphoma.”
The source reports a tissue-based lymphoma diagnosis. It does not report immunophenotyping that establishes T-cell lineage in this individual cat.
EvidenceLevel C — Preliminary evidenceConfidence 100/100
Repeat hematology documented 81,500 leukocytes/µL and 69,000 eosinophils/µL, with no immature peripheral eosinophils observed.
Excerpt verified in the source — verbatim, in the source's own language“On repeat examination, leukocyte counts doubled to 81,500 leukocytes/µL, with a marked increase in absolute eosinophil count (69,000/µL). All eosinophils were segmented, with no immature forms observed.”
This documents extreme peripheral eosinophilia in the reported case. Mature morphology alone does not establish whether the eosinophilia is reactive or clonal.
EvidenceLevel C — Preliminary evidenceConfidence 100/100
The bone marrow profile was consistent with reactive eosinophilic hyperplasia, but cytomorphology alone could not exclude chronic eosinophilic leukemia.
Excerpt verified in the source — verbatim, in the source's own language“This profile is consistent with reactive (secondary) eosinophilic hyperplasia; however, a primary clonal disorder, such as chronic eosinophilic leukemia, cannot be excluded based solely on cytomorphological criteria.”
The marrow supports a reactive interpretation without definitively excluding a primary eosinophilic neoplasm. The authors reiterate this diagnostic limitation in the discussion.
Open questionConfidence 100/100
The exact pathophysiology of lymphoma-associated hypereosinophilia in cats remains poorly understood.
The discussion presents cytokine-mediated explanations as proposed mechanisms extrapolated from feline, canine, and human cases. It does not demonstrate cytokine production by this cat's lymphoma.
Provenance
Source: Feline paraneoplastic hypereosinophilic syndrome associated with lymphocytic intestinal lymphoma.
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