Large granular lymphocytic leukaemia complicated with histiocytic sarcoma in a dog

A 10-year-old castrated male Golden retriever, weighing 36.3 kg was referred for evaluation owing to a decline in general condition. Findings from the complete blood count revealed a marked lymphocytosis (113000/ml). Examination of Wright-Giemsa-stained films of peripheral blood revealed the presence of large granular lymphocytes (LGL). Seventy-two per cent (81360/ml) of the lymphocytes were found to be 12-17 microm in diameter, containing nuclei with mature clumped chromatin and abundant lightly basophilic cytoplasm with a variable number of fine azurophilic granules. Based on these findings this case was diagnosed as LGL leukaemia. As a result of multiple-agent chemotherapy, the markedly elevated levels of lymphocytes gradually decreased to 7500/ml on day 122 and the patient maintained a good quality of life for the following 3 months. However, on around day 237, a soft, raised, bosselated mass on the labial region was noted. The dog was diagnosed as having histiocytic sarcoma based on cytological and histological examination of the mass. Shortly after diagnosis, the dog developed sudden onset of central nervous system signs and died on day 270. A common outcome of canine LGL is the development of acute blast crisis or lymphoma. However, this case was notable for complication with histiocytic sarcoma from another origin.