An overview of canine histiocytic disorders - Veterinary Medicine
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An overview of canine histiocytic disorders
The disorders that arise from histiocyte proliferation range from benign, self-resolving lesions to malignant, life-threatening sarcomas and include a newly identified splenic and bone marrow macrophage disorder. These clinicians give you the information you'll need to readily differentiate and manage these disorders.


Clinical staging

Figure 7A & 7B. Left lateral (7A) and ventrodorsal (7B) radiographs of a 12-year-old intact male golden retriever with disseminated histiocytic sarcoma. A soft tissue opaque nodule is present in the right middle lung lobe (arrows), and more ill-defined, irregularly shaped soft tissue infiltrates are present in the lung caudal to the nodule. (Radiographic interpretation courtesy of Dr. Justin Goggin, DACVR.)
Complete clinical staging with radio graphs of the abdomen, thorax, limbs, and axial skeleton combined with abdominal and thoracic ultrasonography is valuable for evaluating the extent of the disease. The most common thoracic radiographic abnormalities in dogs with disseminated histiocytic sarcoma are sternal, bronchial, hilar, or mediastinal lymphadenopathy and generalized thymic enlargement.23,39 Pulmonary changes (consolidation, nodular opacities, diffuse pulmonary infiltrates) (Figures 6, 7A, & 7B) and pleural effusion have also been noted.23,39 Abdominal abnormalities are nonspecific and include hepatomegaly,23,39 splenomegaly,23,39 splenic masses (Figure 8),23 abdominal lymphadenopathy,23 and ascites.39 Aggressive soft tissue lesions may lead to regional osteolysis; however, survey spinal radiographs are typically normal in dogs presenting with neurologic deficits. Myelography may reveal intradural lesions or extradural compressive lesions in dogs with neurologic manifestations.23

Figure 8. A lateral abdominal radiograph of an 11-year-old neutered male mixed-breed dog with histiocytic sarcoma of the spleen. Note the smoothly marginated, spherical mass (arrow) arising in the midventral abdomen, consistent with a splenic mass. Serosal detail is good, consistent with a lack of peritoneal fluid. (Radiographic interpretation courtesy of Dr. Justin Goggin, DACVR.)
The ultrasonographic features of canine disseminated histiocytic sarcoma are nonspecific, with most abnormalities reported in the spleen and liver.40 The kidneys, adrenal glands, pancreas, ovaries, and gastrointestinal tract may be affected as well. Well-defined hypoechoic nodules in the spleen (Figure 9) associated with disseminated histiocytic sarcoma are similar to those seen with lymphoma, extramedullary hematopoiesis, abscessation, and lymphoid hyperplasia.40 Liver involvement is less consistent, and lesions of variable echogenicity (Figure 10) contribute to generalized hepatomegaly.40 Although the ultrasonographic appearance of disseminated histiocytic sarcoma is not unique, ultrasonography is useful in guiding fine-needle aspiration to aid in diagnosis.


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