Epidemiology, pathology, and genetics of histiocytic sarcoma in the Bernese mountain dog breed

Abstract

Histiocytic sarcoma (HS) refers to a highly aggressive and frequently disseminated neoplastic disease belonging to the class of canine histiocytic proliferative disorders. Disseminated HS (previously called malignant histiocytosis) is highly breed specific, with Bernese mountain dogs (BMDs), rottweilers, and retrievers having a high prevalence with a frequency of approximately 25% in the BMD breed. We collected DNA samples and clinical information from 800 BMDs, of which 200 are affected by HS. To better characterize the physiopathology and epidemiology, an in-depth analysis of 89 BMD cases has been performed. The mean age of onset was 6.5 years, males and females being equally affected. The clinical features, biochemical parameters, and pathological features have been determined. The life span after diagnosis has been estimated to be 49 days. A large BMD pedigree of 327 dogs, 121 of which are affected, was assembled. Using a subset of 160 BMDs, encompassing 21 complete sibships, we now propose an oligogenic transmission mode of the disease. Whole-genome linkage scans as well as association studies using a case/control analysis, in parallel with expression profiling of neoplastic versus normal histiocytes, are all underway. Altogether, these complementary approaches are expected to localize the genes for HS in the BMD, leading to advances in our knowledge of histiocyte diseases in dogs and humans.

Figure 1

Pathological features of disseminated HS: multiple tumor masses affecting the skin, lung, and spleen. (This figure appears in color in the online version of Journal of Heredity.)

Figure 2

Histopathological and immunohistochemical features of HS. Left: neoplastic proliferation of a pleomorphic population of large round uni- or multinucleated cells, with marked atypia and high mitotic index; hemalun–eosin staining; bar = 30 μm. Right: neoplastic cells expressing the leukocyte CD18 marker (immunoperoxidase reaction, diaminobenzidine as chromogen, hematoxylin counterstaining); bar = 30 μm. (This figure appears in color in the online version of Journal of Heredity.)

Figure 3

A portion of 650 dogs of the BMD family segregating HS. (This figure appears in color in the online version of Journal of Heredity.)

Figure 4

Illustration of the popular sire effect in the population of French BMDs: Only 5.4% of sires participate to the next generation (dogs in the rectangle), of which only 0.78% of sires (dog in the square) produce more than 50 % of the next generation (generation n + 1). (This figure appears in color in the online version of Journal of Heredity.)