B-Cell Lymphoma in a Horse with Associated Sézary-like Cells in the Peripheral Blood

Abstract

A 22-year-old Appaloosa gelding was examined at the Veterinary Medical Teaching Hospital, University of Florida, with a 2-week history of inappetence, lethargy, and ventral edema. Cutaneous nodules developed on the neck and lateral thoracic region several days before presentation. The horse was quiet, alert, and responsive on initial examination. The horse had tachycardia (80 beats per minute) and mild tachypnea (36 breaths per minute). A grade I of VI holosystolic murmur was noted on the left side on thoracic auscultation. Both conjunctiva had moderate chemosis and the sclera was mildly icteric. Pitting edema was noted in the ventral abdomen and prepuce. Rectal examination revealed firm nodules associated with the left kidney and root of the mesentery. Significant abnormalities on CBC included a normocytic, normochromic anemia with a hematocrit of 21% (reference range, 32-53%), hemoglobin concentration of 8.6 g/dL (reference range, 11-17 g/dL), mean cell hemoglobin concentration of 35 g/dL (reference range, 34-37g/dL), and mean cell volume of 42 g/dL (reference range, 43-54 g/dL). A marked leukocytosis (54.9 ϫ 10 9 /L; reference range, 5.2 ϫ 10 9 -13.9 ϫ 10 9 /L) and lymphocytosis (43.4 ϫ 10 9 /L; reference range, 1.0 ϫ 10 9 -5.0 ϫ 10 9 /L) were also noted. Lymphocytes in the peripheral blood were a pleomorphic population of cells, many of which contained cerebriform nuclei, clumped chromatin, and scant amounts of basophilic cytoplasm (Fig 1). These cells had a distinct resemblance to the Sézary cells sometimes seen in humans and dogs with cutaneous T-cell lymphoma (mycosis fungoides).1,2 No other leukocyte abnormalities were observed. Serum creatinine concentration was above reference range (2.4 mg/dL; reference range, 1.2-1.9 mg/dL) and serum total protein concentration was 8.6 g/dL (reference range, 5.7-7.9 g/dL) with hyperglobulinemia (6.2 g/dL; reference range, 2.6-4.0 g/dL). Protein electrophoresis revealed a monoclonal gammopathy of gamma 2 region with a protein concentration of 4.4 g/dL (reference range, 0.5-1.9 g/dL). Subsequent immunoelectrophoresis identified this protein to be of immunoglobulin G origin.Abdominal ultrasound revealed irregular nodular structures surrounding the left kidney. The liver appeared enlarged, but was of normal architecture and echodensity. The spleen had a mottled appearance. Cytologic preparations of fine-needle aspirates of the cutaneous lesions were very cel- Gainesville, FL 32610-0136; e-mail: polkesa@mail.vetmed.ufl.edu. Submitted May 6, 1999; Accepted August 3, 1999. Copyright ᭧ 1999 lular and consisted of a population of atypical lymphocytes with nuclei ranging from 10 to 20 m in diameter. The nuclei of many of the cells were indented or cleaved, similar to those seen in the peripheral blood. The chromatin appeared moderately condensed and mitotic figures were occasionally observed. The nucleus to cytoplasm ratio was high and the cells had a thin rim of deeply basophilic cytoplasm. Based on these findings, a cytologic diagnosis of cutaneous lymphoid neoplasm was...

Extreme lymphocytosis with myelomonocytic morphology in a horse with diffuse large B‐cell lymphoma

“…Circulating neoplastic lymphocytes with indented, cerebriform nuclei can be seen rarely in dogs with epitheliotropic T‐cell lymphoma and Sézary syndrome. Rare cases of equine lymphoma and Sézary‐like cells in the peripheral blood exist . Interestingly, similar to this case, one such case had a multicentric B‐cell lymphoma with peripheral blood intermediate lymphocytes described as pleomorphic, with cerebriform nuclei.…”

“…The magnitude of lymphocytosis in this case was suggestive of leukemia; however, lack of obvious bone marrow infiltration and histopathologic findings supported a diagnosis of lymphoma with marked peripheral blood involvement. Lymphoma with a mild to moderate leukemic blood picture is not uncommon in horses, but only rare cases with marked leukemic manifestations, as in the present case, have been described . In cases in which immunophenotyping was performed, the majority were T‐cell or presumptive T‐cell lymphomas .…”

“…In cases in which immunophenotyping was performed, the majority were T‐cell or presumptive T‐cell lymphomas . One horse with B‐cell lymphoma and marked peripheral lymphocytosis was reported; however, the lymphoma subtype was not determined …”

Equine lymphoma

“…Other cytological abnormalities reported in the peripheral blood smear of leukaemic horses include Heinz bodies and Sézary cells (medium to large lymphocytes with ceribriform nuclei resembling a monocyte and scant cytoplasm) (Rollins et al . 1991; Polkes et al . 1999).…”

Overview and Lymphoma/Lymphosarcoma

“…Lymphocytic plasmacytic inflammation may be associated with alimentary lymphoma, which some consider a potentially prelymphomatous change. 3,4,10 Nonepitheliotropic cutaneous lymphoma in the dog may be of either B or T lymphocyte phenotype. 3 Cutaneous lymphoma in the dog may be solitary or generalized, and epitheliotropic and nonepitheliotropic forms are described.…”