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-Medicine 0891-6640/99/1306-0019/$3.00/0 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 made. Examination of a bone marrow aspirate revealed mild erythroid hyperplasia with evidence o...

Hematopoietic Neoplasias in Horses: Myeloproliferative and Lymphoproliferative Disorders

“…Although lymphoma is not common in horses, it is the most frequent malignant neoplasm encountered [47, 54, 63]. The incidence of this neoplasia is of 0.7–3.2/ 100,000 horses [35, 61].…”

“…Four categories of lymphoma have been established according to the affected organs and extension: multicentric or generalized, alimentary or intestinal, mediastinal, thoracic or thymic and cutaneous, being the generalized and cutaneous forms the most common [47, 54]. Furthermore, solitary tumors at extranodal sites have been reported in tongue, bladder, leg, and ovary [22, 59, 68].…”

“…More rarely, tumors can invade the upper airways, causing respiratory obstructions and coughing, spinal cord [30], with spinal compression and neurological signs, including paraplegia and hemiplegia, central nervous system [50], heart [50, 54] causing arrhythmias and altered valvular function, and retrobulbar space, with exophthalmos. Given the degree of organ involvement in the multicentric form, this syndrome could be very similar to intestinal lymphoma with metastasis.…”

Internal neoplasia in the horse with special regard to the cytology of body cavity fluid

“…Meyer et al (2006) versuchten diese Unterteilung nachzuvollziehen, was ihnen jedoch nicht gelang. Das Plasmazellmyelom ist eine Neoplasie einer entarteten B-Zelllinie, die eine monoklonale Gammopathie verursacht (Marr 1994, Polkes et al 1999, Barton et al 2004. Dabei sind verschiedene Formen wie das solitäre Plasmozytom, das multiple Myelom, die medulläre Plasmozytose und die Plasmazellleukämie beschrieben.…”

“…In Abwesenheit eines elektrophoretischen γ-Globulinpeaks ist die Diagnose über eine Knochenmarkspunktion oder Organbiopsie zu stellen. In seltenen Fällen ist eine hochgradige Leukozytose mit Lymphozytose und abnormen lymphoiden Zellen im Blut zu finden (Polkes et al 1999). …”