History
A 7-year-old 22-kg (48.4-lb) castrated male mixed-breed dog was evaluated at a university veterinary health center because of a 4-week history of anorexia, tachypnea at rest, and large-bowel diarrhea.
Clinical and Clinicopathologic Findings
On physical examination, the dog was in poor condition with a body condition score of 3/9. Mucous membranes were pale. The dog was mildly tachycardic with a heart rate of 140 beats/min; femoral pulses were strong and synchronous with the heartbeat. Thoracic auscultation revealed no abnormal lung sounds and a resting respiratory rate of 28 breaths/min.
Clinicopathologic analyses revealed microcytic, hypochromic, marked (PCV, 14%; reference interval, 41% to 59%) anemia with moderate regeneration and a mild chronic inflammatory leukogram (neutrophil concentration, 18.2 × 103 neutrophils/μL; reference interval, 2.5 × 103 to 9.3 × 103 neutrophils/μL). The dog had moderately low serum iron concentration (23 μg/dL; reference interval, 73 to 245 μg/dL), a total iron-binding capacity that was normal (367 μg/dL; reference interval, 270 to 530 μg/dL), and mildly high ferritin concentration (595 ng/mL; reference interval, 89 to 489 ng/mL).
Thoracic radiography revealed a severe, diffuse miliary pattern throughout all lung fields; most soft tissue–opacity nodules were 2 to 4 mm in diameter. The cardiac silhouette was within expected limits. Abdominal ultrasonographic findings were unremarkable apart from a 1.4-cm-diameter, hypoechoic nodule in the spleen. A Histoplasma antigen testa was submitted, and the result was negative. Examination of a fine-needle aspirate specimen of the pulmonary parenchyma revealed macrophagic inflammation with a variable density of green-black globular material consistent with hemosiderin (Figure 1).
Photomicrograph of a fine-needle aspirate specimen of the lung (A) and gross photograph of lung tissue (B) of a 7-year-old mixed-breed dog that was evaluated because of a 4-week history of anorexia, tachypnea at rest, and large-bowel diarrhea. In the fine-needle aspirate specimen (A), the predominant cells seen are individual activated macrophages dilated with multiple small discrete clear vacuoles, cellular debris, and a brown-green to blue-black material suspected to be hemosiderin. Modified Wright stain; bar = 25 μm. On the surface of all visible lung lobes (B), there are firm, black and white nodules.
Citation: Journal of the American Veterinary Medical Association 257, 5; 10.2460/javma.257.5.499
The dog was treated empirically with antifungal agents and supplemental iron. Plans were made for repeated thoracic radiography and lung biopsy to be performed after 2 weeks of treatment. The dog was presented to the hospital's emergency service 1 week following initiation of antifungal treatment because of a sudden onset of respiratory distress. At this time, the dog had severe anemia (PCV, 7%). The owner elected euthanasia by injection of pentobarbital and allowed a limited necropsy (ie, gross and histologic examination of the lungs).
On gross examination, the dog had a mild amount of serosanguineous discharge from both nostrils. Diffusely, all the lung lobes had pinpoint to 1-cm-diameter, raised, firm, black and white nodules on the surface and within the parenchyma. The abdominal cavity was not explored.
Formulate differential diagnoses from the history, clinical findings, and Figure 1—then turn the page→
Histopathologic Findings
Approximately 40% of the lung tissue was affected by multifocal, welldemarcated, unencapsulated nodules composed of aggregates of spindle-shaped cells admixed with moderate numbers of macrophages and pools of erythrocytes. Neoplastic cells lined capillary-like structures and vascular channels that contained erythrocytes, fibrin thrombi, and numerous hemosiderin-laden macrophages. The neoplastic cells each had variably distinct borders with scant to moderate amounts of homogeneous eosinophilic cytoplasm and a centrally placed oval nucleus. The nuclei each contained coarsely stippled chromatin with a prominent nucleolus. There was marked anisocytosis and anisokaryosis with 4 to 6 mitotic figures/hpf (400×).
Immunohistochemical analysis revealed that the neoplastic spindle-shaped cells forming the vascular channels were positive for claudin-5 (Figure 2) and negative for the general leukocyte immunohistochemical marker CD18. Grocott-methenamine-silver staining revealed that lung tissue sections were negative for fungal organisms.
Photomicrograph of a section of lung tissue from the dog in Figure 1. The proliferative endothelial cells lining the vascular channels are positive for claudin-5. Claudin-5–specific immunohistochemical reaction; bar = 50 μm.
Citation: Journal of the American Veterinary Medical Association 257, 5; 10.2460/javma.257.5.499
Morphologic Diagnosis and Case Summary
Morphologic diagnosis and case summary: hemangiosarcoma (HSA) confirmed by positive results of immunohistochemical analysis of lung tissue sections for claudin-5 and presence of iron-deficiency anemia (believed to be secondary to chronic hemorrhage) in a dog.
Comments
Hemangiosarcoma is a highly malignant tumor of vascular endothelial cell origin.1,2 It develops more frequently in dogs than in other species, accounting for 5% to 7% of noncutaneous primary malignant neoplasms in dogs.1,2 Among dogs, the mean age at the time of diagnosis of HSA ranges from 8 to 12 years,1 and German Shepherd Dogs, Golden Retrievers, Labrador Retrievers, and Schnauzers are predisposed to development of HSA.1,2 Hemangiosarcoma may affect any tissue in the body; the most common primary sites are the spleen, right atrium and auricle, skin or subcutaneous tissue, and liver.1,2 Other primary sites include kidneys, urinary bladder, prostate, peritoneum, lungs, pulmonary arteries, aorta, muscles, bones, oral cavity, tongue, vertebral bodies, and CNS.1,2
Hemangiosarcoma is a highly metastatic tumor, and > 80% of dogs with HSA have overt evidence of metastatic disease at the initial evaluation. The most common site of metastases are the liver, omentum, mesentery, and lungs.2,3 As many as 25% of dogs with splenic masses have concurrent cardiac masses.1–3 Clinical signs vary from subtle weakness to acute collapse associated with hemorrhage of a visceral mass,2,3 and an affected dog may have various clinical signs associated with bleeding at the primary or metastatic tumor sites. For the dog of the present report, the lungs were the only organ evaluated histologically; therefore, it was unknown whether the lungs were the site of a primary pulmonary HSA or metastatic HSA from a right auricular, splenic, or other visceral primary tumor.
In the dog of the present report, the most profound clinical features were persistent tachypnea and anorexia. At the initial evaluation, differential diagnoses for the miliary pattern observed on thoracic radiographs included systemic fungal infection (most likely histoplasmosis given the geographic environment) and metastatic neoplasia. A Histoplasma antigen testa was used as a noninvasive test to rule out fungal disease, although the results of this test were not available for > 1 week. Given the lack of a solid mass that could be identified as a primary tumor, examination of a fine-needle aspirate specimen of the dog's lungs was performed to search for fungal organisms or neoplastic cells. The examination of a fine-needle aspirate specimen did not reveal fungal organisms or neoplastic cells. Because of the predominance of hemosiderin-laden macrophages, differential diagnoses of either primary or secondary pulmonary hemorrhage were considered. Underlying suspected neoplastic causes were metastatic HSA or hemophagocytic histiocytic sarcoma. Surgical biopsy of the dog's lung tissue was recommended, but the dog was euthanized before this procedure could be performed.
As illustrated by the case described in the present report, antemortem diagnosis of HSA is often a challenge. Presurgical diagnostic testing, including a CBC, serum biochemical profile, and urinalysis, and thoracic and abdominal imaging (eg, thoracic radiography, abdominal ultrasonography, and whole-body CT) are often performed when HSA is suspected; however, none of those tests can distinguish benign from malignant neoplasms. The dog of the present report had microcytic, hypochromic, moderately regenerative anemia. Regenerative anemias may be associated with HSA or histiocytic sarcoma, and various RBC morphologies have been reported for both diseases.3 However, the presence of anemia alone cannot distinguish HSA from histiocytic sarcoma. Examination of fine-needle aspirate specimens of gross lesions may allow for exclusion of other neoplastic diseases (eg, lymphoma or metastatic carcinomas), but overall agreement between cytologic and histopathologic findings for HSA has been reported as accurate in only 17 of 56 dogs in 1 retrospective study.4
Histologically, HSA can have either irregular vascular channels or expanded caverns, both of which are lined by variably differentiated neoplastic endothelial cells.5 The morphological features of HSA can sometimes overlap with those of other sarcomas, and differentiation among these tumors may require immunohistochemical analyses.5–7 Common endothelial markers used to identify canine HSAs from other sarcomas include CD31 and factor VIII–related antigen, although these markers do not differentiate between tumors of lymphatic or blood vessel origin.7 Claudin-5 is a vascular-specific transmembrane protein that is expressed in neoplastic endothelial cells of cavernous, capillary, and solid tumor types.7 In the case described in the present report, lung tissue sections were positive for this marker, which enabled differentiation of HSA from histiocytic sarcoma or other metastatic neoplastic disease.
Initial treatment of dogs with HSA involves surgery, although this is mainly palliative. Median survival time for dogs with visceral HSA treated with surgery alone ranges from 19 to 86 days.2,3 In the dog of the present report, the primary tumor may possibly have been splenic or cardiac in origin, although there was no evidence of hemorrhagic peritoneal effusion, cardiac silhouette enlargement, pericardial effusion, or gross cardiac masses during the limited postmortem examination permitted by the owner. Primary pulmonary angiosarcoma has been described in the human medical literature, with the diagnosis typically made by exclusion of other primary tumor sites.8 For the dog of the present report, surgical excision of the HSA would not have been possible given the diffuse pulmonary involvement.
Chemotherapy is recommended as an adjuvant treatment for patients with HSA that are treated surgically. Doxorubicin or its analog epirubicin has been used as a single agent or in various combinations with cyclophosphamide, vincristine, or dacarbazine.9–12 The benefit of metronomic chemotherapy with cyclophosphamide, etoposide, and piroxicam is comparable to that of single-agent doxorubicin chemotherapy.13 The benefit of chemotherapy in the treatment of gross disease is mostly unknown, although 1 retrospective study14 of dogs with measurable subcutaneous HSA lesions revealed an overall response rate of 38.8% with doxorubicin-based chemotherapy. An additional adjuvant treatment option includes single-agent administration of polysaccharopeptide, which has been reported to improve survival times in dogs with HSA.15 Overall prognosis for dogs with visceral HSA is poor, with most reports citing a median survival time of 85 to 199 days.9–11,15
Footnotes
MiraVista Diagnostics, Indianapolis, Ind.
References
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