Atypical lymphosarcoma in a cow.

Abstract

A FOUR-year-old Angus cow was presented for evaluation of a large mass in the ventral caudal cervical region. The mass was first observed by the owner the day before presentation. Two weeks prior to presentation, the cow delivered her third calf. The cow was dull and thin (body condition score 4/10). The respiratory rate was 40 breaths/min, the rectal temperature was 39 5°C and the heart rate varied from 96 to 60 beats/min during the physical examination. Rectal examination was normal. A firm mass extended from the left thoracic inlet rostral 40 cm in the left jugular furrow. The mass measured approximately 30 cm in a dorsoventral direction and extended outward from the normal cervical contour approximately 10 cm. The exact size of the mass could not be determined because palpation did not reveal the deep extent of the mass. Biopsy samples were obtained for histological examination and a serum sample was tested for antibodies against bovine leukosis virus (BLV). Haematology also was performed. Histological examination of biopsy samples revealed dense sheets of lymphoid cells occasionally supported by a scant reticular stroma and extensive replacement of skeletal muscle by tumour cells. The serum agar gel immunodiffusion (AGID) test for BLV was negative. Abnormal findings on haematological examination included mild anaemia (PCv 26 per cent) and hyperproteinaemia (8.7 g/dl). Total leucocyte, neutrophil, lymphocyte and monocyte counts were within normal ranges. No lymphocytes with abnormal morphology were observed in peripheral blood. Economically feasible and efficacious treatment was unlikely and as the cow was unlikely to pass post mortem slaughter examination she was returned to the care of her owner. The authors anticipated that the cow's condition would deteriorate rapidly; however, the cow appeared comfortable and it was felt that continued nursing would benefit the calf. Eighteen days following the initial examination the cow was presented for euthanasia. The mass appeared as previously described and there was a moderate swelling (5 cm x 5 cm) in the intermandibular space. No other abnormalities were detected on physical examination. Intermittent bloat was observed and an indwelling ruminal trocar was placed to prevent ruminal tympany. Three days following presentation the cow was observed regurgitating and she was enthanased the following day. Temperature, pulse and respiratory rates were within normal limits. Post mortem examination revealed a large (40 cm x 33 cm x 20 cm) firm subcutaneous mass, primarily at the left thoracic inlet. The mass completely encompassed, but did not invade, the trachea and oesophagus, however adjacent cervical musculature was involved. The mass was mottled, pale, white-grey and red and the cut surface bulged and had multiple distinct yellow-brown areas surrounded by a thin rim of haemorrhage. Microscopic examina-