Chronic eosinophilic leukemia in a cat: cytochemical and immunophenotypical features

Abstract

A 3-year-old, male, domestic shorthaired cat was presented with a 3-day history of anorexia and depression. The cat was moderately dehydrated, had pale, slightly icteric, mucous membranes, oral ulcerations, and mild hepatosplenomegaly. A feline leukemia virus (FeLV) antigen test was positive. CBC results obtained at initial presentation included severe normocytic, normochromic, nonregenerative anemia, severe thrombocytopenia, and marked leukocytosis (>100,000/microL) with 77% eosinophils. After 15 days of treatment with prednisone and doxycycline, the cat had persistent severe nonregenerative anemia (HCT 3.4%), thrombocytopenia (28,000/microL), and extreme eosinophilia (total eosinophils, 123.1 x 10(3)/microL; segmented 103.0 x 10(3)/microL; immature 20.1 X 10(3)/microL). Cytologic examination of aspirates from bone marrow, liver, lymph nodes, and spleen revealed a predominance of mature and immature eosinophils, many with dysplastic changes. The M:E ratio was 96.4. On histopathologic examination, multiple organs were infiltrated by eosinophilic granulocytes. Neoplastic cells in blood and bone marrow stained positive for alkaline phosphatase and were negative for myeloperoxidase, chloroacetate esterase, and alpha-naphthyl acetate esterase. On flow cytometric analysis of peripheral blood, the neoplastic cells were positive for CD11b and CD14. These findings were consistent with chronic eosinophilic leukemia. To our knowledge, this is the first report of chronic eosinophilic leukemia in a cat associated with naturally acquired FeLV infection, in which flow cytometry was used to characterize the neoplastic cells.

Hypereosinophilic Syndrome in Two Cats

“…Remarkable eosinophilia, as seen in the cats reported here, is characteristically observed in eosinophilic proliferative disorders such as HES and chronic eosinophilic leukemia (CEL) [4,6,14]. Both diseases have a similar clinical presentation in cats that often reflects gastrointestinal involvement (anorexia, weight loss, vomiting, and diarrhea) [4,6,14,19].…”

“…Both diseases have a similar clinical presentation in cats that often reflects gastrointestinal involvement (anorexia, weight loss, vomiting, and diarrhea) [4,6,14,19]. Feline CEL has been distinguished from HES in the points of the presence of blasts in the peripheral blood, morphological abnormalities and immaturity with abnormal granulation in the eosinophilic lineage, high M/E ratio in the bone marrow, and marked anemia [4,6,14].…”

“…As the therapy for feline HES and CEL, immunosuppressive doses of corticosteroids have been used; however, responses to the therapy were uniformly poor [4,14,19]. There has been only one reported feline case in which the blood eosinophil count could be controlled for more than 28 months by medication with prednisolone and hydroxycarbamide [9].…”

“…Feline CEL has been distinguished from HES in the points of the presence of blasts in the peripheral blood, morphological abnormalities and immaturity with abnormal granulation in the eosinophilic lineage, high M/E ratio in the bone marrow, and marked anemia [4,6,14]. Nevertheless, the clinical course of both diseases is similar, and death occurs mainly from infiltration into multiple organs (gastrointestinal tract, spleen, liver, lymph nodes, heart and lungs) [4,6,14,19]. Organ damage and dysfunction can be caused by a release of cytotoxic substances from eosinophils such as eosinophil cationic protein, major basic protein, eosinphil-derived neurotoxin, oxydating molecules including eosinophil peroxidase and free oxygen radicals, and enzymes including elastase and collagenase [12,13].…”

Prognostic Markers for Myeloid Neoplasms

“…16 Chronic eosinophilic leukemia, which is by definition clonal, can be difficult if not impossible to distinguish from HES. 95 Chronic eosinophilic leukemia has been reported in 35,48,58 Hypereosinophilia, attributed to either inflammation or paraneoplastic interleukin-5 production by lymphoma, was more common than CEL. 48 CEL, but not hypereosinophilia, was associated with immature or abnormal eosinophils in circulation, M/E ratios exceeding 10:1, and anemia.…”