Splenic myelolipoma in a dog

ABSTRACT: Myelolipoma is a benign neoplasm composed of mature adipocytes and hematopoietic elements. This tumor is rare in dogs and cats and can develop in several organs and tissues. This report describes a case of splenic myelolipoma in a dog characterizing its clinical-pathological and ultrasonography aspects. A 9-year-old, female, mixed-breed, castrated dog was referred to the veterinary hospital with increased abdominal circumference. Ultrasonography revealed splenomegaly with masses of not measurable dimensions along the entire length of the parenchyma. The spleen was removed, and a fragment was sent for histopathological analysis. Macroscopically, the spleen was enlarged, with irregularly nodular growths that project above the surface of the organ. Nodules were red with small yellow areas. Microscopically, the spleen was effaced by a well-demarcated and not encapsulated mass composed of histologically well-differentiated neoplastic adipose tissue with islands and nests of varying proportions of hematopoietic elements. Histological examination confirmed the diagnosis of myelolipoma. Myelolipomas are observed on ultrasound images as hyperechoic masses or nodules with homogeneous echo texture. Here, ultrasound appearance involved mixed echogenicity and heterogeneous echotexture, due to the mixture of fat and non-fatty material components of the tumor.