Histiocytic sarcoma (HS) is an aggressive neoplasm of dogs. Over-representation has been documented in several breeds, including Bernese mountain dogs, flat-coated retrievers, golden retrievers, and Rottweilers. The purpose of this retrospective study was to describe a series of miniature schnauzers (MS) diagnosed with HS in the UK and assess whether they were over-represented when compared to the hospital population.

Medical records of MS with a cytological or histopathological diagnosis of HS between January 2010 and March 2017 were reviewed. Breed predisposition was assessed with odds ratios, using the total number of hospital admissions for each breed without HS admitted during the study period as controls. This was also performed where two or more cases with HS were recorded for a particular breed.

Ten MS were diagnosed with HS during the study period, making them over-represented among the hospital population (odds ratio=8.98 [95% CI 4.64–17.41]). Seven were diagnosed with primary pulmonary HS based on the presence of a large pulmonary mass with or without evidence of intrathoracic metastasis or abdominal involvement, though only five exhibited overt respiratory signs. No patients had solitary HS. Five patients were treated with chemotherapy (lomustine +/- epirubicin) but an aggressive clinical course was found in all patients. Median survival time of all patients was 54 days (range: 0–232 days). Several other previously reported breeds were also noted to be predisposed to HS.

MS, in addition to previously reported breeds, were over-represented amongst dogs with HS in this patient population. Primary pulmonary involvement was common and patients presented with advanced disease, though some patients had no overt respiratory signs. The prognosis appears to be poor despite chemotherapy.

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