Clinical, histopathological and immunophenotypical findings in five horses with cutaneous malignant lymphoma.

This study documents the clinical, histopathological, immunohistochemical and flow-cytometric findings in five horses with cutaneous non-epidermotropic malignant lymphoma (ML). The median survival time after discovery of the first subcutaneous nodules was 3.8 years (range 2-5 years: n=4). Histologically, the cutaneous ML had a pleiomorphic structure and contained a mixture of large reticulo-endothelial cells, medium-large sized lymphoid cells with a rounded nucleus and small nucleoli, many medium sized lymphoid cells with irregular nuclei, and some small lymphoid cells. Immunohistochemically (IHC) the lymphoid cells were positive for the pan-T-lymphocyte marker CD3 but negative for the B-lymphocyte markers CD21 and kappa and lambda immunoglobulin light chains. Although routine haematological examination revealed no abnormalities in the horses with cutaneous ML, changes in the peripheral blood lymphocyte population were apparent flow-cytometrically. Compared to clinically healthy horses, a decreased total percentage of cells was recorded in the lymphocyte gate. In three horses with cutaneous ML, an increase in CD4 positive cells was noticed in the monocyte gate. Flow-cytometric analysis of tumour cells collected by fine needle aspiration (FNA) suggested that the cutaneous MLs consisted primarily of CD4 and CD8 positive T-lymphocytes. The results were compared to those of a monomorphic multicentric T- and a monomorphic multicentric B-cell lymphoma. The results of immunohistochemistry and flow-cytometry were largely but not completely in accordance. In conclusion, the results of this study suggest that cutaneous non-epitheliotropic malignant lymphomas in the horse are of T-cell origin and that, after improvement of its accuracy, flow cytometric analysis of FNAs might become a useful aid to rapid tumour identification.

[Malignant melanoma of the pelvis as a possible cause of pelvic limb lameness in two gray mares]. / Maligne melanoom in het bekken als mogelijke oorzaak van een bewegingskreupelheid in het achterbeen bij twee schimmelkleurige paarden.

Two grey mares, a 12-year-old Arabian and a 13-year-old Lippizaner cross, were referred for chronic pelvic limb lameness and abduction of the limb during the non supporting phase of the stride. The clinical examination revealed melanomas under the tail and on the perineum, and oedema of the proximal lame limb. A mass in the pelvic area was detected on rectal palpation. Laparoscopy was performed and the provisional diagnosis of malignant melanoma was made. Histological examination of the biopsy taken under laparoscopic control from the mass in the pelvis confirmed the diagnosis of malignant melanoma. In the postmortem examination a large black mass in the pelvis and metastases in several organs were diagnosed. The process under the tail showed microscopically the characteristics of dermal melanomatosis. The metastases showed the appearance of a malignant melanoma. The lameness and abduction during the non supporting phase of the stride were possibly caused by a combination of pain, a mechanical limitation, and paresis/paralysis. When an older grey horse with melanomas on the predilection sites is submitted with pelvic limb lameness and abduction of the limb during the non supporting phase of the stride, a malignant melanoma in the pelvis is one of the differential diagnoses and a rectal examination should be performed. Diagnostic laparoscopy in the standing horse can be useful to confirm the provisional diagnosis.

[Bronchoaveolar lavage for the diagnosis of lower airway disorders in horses]. / Bronchoalveolaire lavage (bal) in de diagnostiek van diepere luchtwegaandoeningen bij het paard.

Equine pulmonary disease and especially the terminology of lower airway disease have been subject to discussion. Besides established terms such as 'Chronic Obstructive Pulmonary Disease' (COPD) and Chronic bronchitis, the term 'small airway disease' (SAD) has been introduced, for respiratory disease with inflammation in the lower airways in combination with exercise intolerance. Bronchoalveolar lavage (BAL) enables the practitioner to diagnose SAD in an early stage when there are no other signs such as coughing or exudate in the trachea. The BAL fluid is microscopically examined after centrifugation. BAL cytology, especially neutrophilia, eosinophilia, and an increase in mast cells, is important, not only to decide whether SAD is present but also to determine in the choice of therapy.