Pathology in Practice

Whitney M. Zoll Diagnostic Center for Population and Animal Health, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48910.

Search for other papers by Whitney M. Zoll in
Current site
Google Scholar
PubMed
Close
 DVM
,
Chee Bing Ong Diagnostic Center for Population and Animal Health, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48910.

Search for other papers by Chee Bing Ong in
Current site
Google Scholar
PubMed
Close
 BVSc, MS
,
Rebecca C. Smedley Diagnostic Center for Population and Animal Health, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48910.

Search for other papers by Rebecca C. Smedley in
Current site
Google Scholar
PubMed
Close
 DVM, MS
, and
Scott D. Fitzgerald Diagnostic Center for Population and Animal Health, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48910.

Search for other papers by Scott D. Fitzgerald in
Current site
Google Scholar
PubMed
Close
 DVM, PhD

History

A 6-year-old 29.9-kg (65.8-lb) castrated male Golden Retriever was evaluated because of weight loss, weakness, and inappetence, all of 1 month's duration, as well as vomiting and diarrhea of 2 weeks’ duration.

Clinical and Gross Findings

On physical examination at the referral clinic, the dog had signs of depression and was slightly dehydrated. Clinicopathologic analyses revealed mild leukocytosis (16,700 WBCs/µL; reference interval, 4,000 to 15,500 WBCs/μL) characterized by mild neutrophilia (13,527 neutrophils/µL; reference interval, 2,060 to 10,600 neutrophils/µL) and mild monocytosis (1,670 monocytes/μL; reference interval, 0 to 840 monocytes/µL). Hyperproteinemia (8.1 g/dL; reference interval, 5.0 to 7.4 g/dL), hyperglobulinemia (5.0 g/dL; reference interval, 1.6 to 3.6 g/dL), high serum aspartate aminotransferase activity (89 U/L; reference interval, 15 to 66 U/L), high serum alanine aminotransferase activity (250 U/L; reference interval, 12 to 118 U/L), high serum alkaline phosphatase activity (1,203 U/L; reference interval, 5 to 131 U/L), high serum γ-glutamyltransferase activity (32 U/L; reference interval, 1 to 12 U/L), hyperbilirubinemia (0.6 mg/dL; reference interval, 0.1 to 0.3 mg/dL), and hypoglycemia (53 mg/dL; reference interval, 70 to 138 mg/dL) were reported. Serum trypsin-like immunoreactivity (TLI) testing was performed to assess exocrine pancreatic function and the result was within reference limits. The dog was administered IV fluid therapy (amount, rate, and type of fluids not available), an injection of maropitant citrate (dose not available), and ampicillin (250 mg, PO, q 12 h). The dog was discharged from the hospital, but 5 days later, it developed rapid shallow breathing, was shaking, and died.

The dog was immediately submitted for necropsy. The body of the spleen contained a 6.5 × 7 × 4-cm, multilobulated, mottled yellow-tan to dark red mass (Figure 1). On the capsular surface of all hepatic lobes, there were numerous, clearly delineated, slightly raised, pale yellow nodules (0.5 to 2 cm in diameter) with depressed centers. These nodules extended into and slightly compressed the underlying, hepatic parenchyma. There was accentuation of the lobular pattern within the remaining hepatic parenchyma.

Figure 1—
Figure 1—

Photographs of the spleen and liver from a dog that was evaluated for chronic weight loss, anorexia, and vomiting. A—A large, expansile, multinodular, mottled tan to dark red mass is present in the body of the spleen. Bar = 5 cm. B—Notice the multifocal to coalescing, slightly raised, umbilicated, pale yellow masses in the liver. Bar = 5 cm. Inset—The masses extend into, efface, and partially compress the underlying hepatic parenchyma, which has an accentuated lobular pattern.

Citation: Journal of the American Veterinary Medical Association 249, 3; 10.2460/javma.249.3.279

Formulate differential diagnoses from the history, clinical findings, and Figure 1—then turn the page→

Histopathologic Findings

Sections of the spleen and liver as well as other major body organs were routinely processed and histologically examined. The normal parenchyma of both the liver and spleen were obliterated by a non-encapsulated, poorly delineated, and markedly infiltrative proliferation of neoplastic mesenchymal cells. The neoplastic cells were arranged in dense bundles and sheets within abundant collagenous stroma (Figures 2 and 3). The neoplastic cells were polygonal to spindloid, had variable amounts of eosinophilic cytoplasm, and had indistinct cell borders. The nuclei were oval to fusiform, had stippled to condensed chromatin, and contained irregular, variably sized nucleoli. There were multinucleated neoplastic cells randomly scattered throughout the neoplastic cell population in each organ. Anisocytosis and anisokaryosis were marked, and mitoses [4/10 hpf (40×)] were present. Multifocal areas of necrosis and scattered lymphocytes and plasma cells were also noted. In the liver, there was atrophy and dissociation of remaining hepatocytes entrapped within the neoplasm. Neoplastic cells were not identified in any of the other tissues examined.

Figure 2—
Figure 2—

Photomicrograph of a section of the liver from the same dog in Figure 1. Neoplastic cells have infiltrated and extensively effaced the hepatic parenchyma. There is atrophy and dissociation of remaining hepatocytes entrapped within the neoplasm. H&E stain; bar = I mm. Inset—Higher magnification of the neoplastic spindloid cells, which infiltrate hepatic sinusoids. Anisocytosis and anisokaryosis are marked. H&E stain; bar = 200 μm.

Citation: Journal of the American Veterinary Medical Association 249, 3; 10.2460/javma.249.3.279

Figure 3—
Figure 3—

Photomicrographs of sections of the neoplastic mass in the spleen of the dog in Figure 1. A—In the spleen, neoplastic cells are stellate to spindloid and arranged in dense bundles and sheets with a small amount of collagenous stroma. H&E stain; bar = 500 μm. B—Neoplastic cells (asterisk) are negative for CD 18. Notice the CD 18-positive brown perimembranous labeling of interstitial dendritic cells between the neoplastic cells. CD 18-specific stain with diaminobenzidine chromogen (brown); bar = 500 μm. C—Neoplastic cells are negative for CD31. Notice the CD31-positive brown perimembranous labeling of the endothelial cells lining vessels within the neoplasm. CD31-specific stain with diaminobenzidine chromogen (brown); bar = 50 μm. D—Neoplastic cells have strong red cytoplasmic labeling for vimentin. Vimentin-specific stain with amino-ethyl-carbazol chromogen (red); bar = 50 μm.

Citation: Journal of the American Veterinary Medical Association 249, 3; 10.2460/javma.249.3.279

Immunohistochemical labeling for desmin, vimentin, smooth-muscle actin, CD18, factor VIII related-antigen, CD31, and KIT were used to further classify the neoplasm. The neoplastic cells had strong positive cytoplasmic immunolabeling for vimentin and were negative for all of the other markers.

Morphologic Diagnosis and Case Summary

Morphologic diagnosis and case summary: nonangiomatous, nonlymphomatous splenic sarcoma with hepatic metastasis in a dog.

Comments

In the dog of the present report, the spleen contained a large single mass, and the liver contained numerous smaller multifocal masses. Thus, the primary neoplasm was determined to be of splenic origin with metastasis to the liver. Primary malignant splenic neoplasms include several types, the most common being hemangiosarcoma, lymphosarcoma, and other splenic mesenchymal neoplasms that fall into the category of nonangiomatous, nonlymphomatous splenic sarcomas.1 The nonangiomatous, nonlymphomatous splenic sarcoma group of neoplasms includes leiomyosarcoma, fibrosarcoma, undifferentiated sarcoma, myxosarcoma, leiomyoma, liposarcoma, osteosarcoma, histiocytic sarcoma, mesenchymoma, lipoma-myelolipoma, and malignant fibrous histiocytoma.1 On the basis of the gross findings, differential diagnoses for the case described in the present report included soft-tissue sarcoma and round cell tumor, such as histiocytic sarcoma and lymphoma. Hemangiosarcoma was considered to be less likely because the masses were not especially hemorrhagic. Given the histologic findings, primary differential diagnoses were histiocytic sarcoma, undifferentiated sarcoma, and leiomyosarcoma.

To further classify this neoplasm, immunohistochemical analyses for desmin, smooth-muscle actin, CD18, factor VIII-related antigen, CD31, KIT, and vimentin were performed. As expected, the smooth muscle cells of the vessels within the liver and spleen as well as the smooth muscle trabeculae within the spleen had cytoplasmic labeling for smooth-muscle actin and desmin (internal positive control); however, the neoplastic cells did not label for either marker. Thus, a neoplasm of smooth muscle origin was less likely. Many individually scattered cells throughout the neoplasm in the spleen, including resident lymphocytes and hematopoietic cells in the more normal splenic parenchyma, and Kupffer cells in the liver had perimembranous cytoplasmic labeling for CD18; however, the identified neoplastic cell population had no label uptake (Figure 3). On the basis of the pattern of labeling in the splenic sections, the cells within the neoplasm that were positive for CD18 were primarily interstitial dendritic cells and occasionally scattered lymphocytes. Interstitial dendritic cells were often difficult to visualize in H&E-stained sections of the spleen, but their dendritic processes were highlighted by the brown immunolabeling for CD18. Results of immunolabeling for CD18 (a generic leukocyte marker) as well as labeling results for other more specific markers (eg, CD1, CD4, CD11c, CD11d, CD204, and Thy-1) is often used to support a diagnosis of histiocytic sarcoma in dogs.2 Other round cells, such as lymphocytes, mast cells, and plasma cells, are also often CD18 positive. Thus, if neoplastic cells are deemed to be positive for CD18, testing with immunohistochemical markers to rule out other round cell tumors should be performed before a diagnosis of histiocytic sarcoma is reached. Labeling for CD204 (histiocyte marker) also can be used for the diagnosis of histiocytic sarcoma. Interstitial dendritic cells are often numerous in various types of splenic and soft-tissue sarcomas as well as some other neoplasms (eg, melanomas). Side-by-side comparison sections of such a mass stained with H&E stain and immunohistochemically labeled for CD18 is often needed to identify the underlying neoplastic cell population before interpretation of the labeling. Histiocytic sarcoma is characterized by sheets of cells that have perimembranous labeling for CD18, which creates a honeycomb appearance. It is important to note that for the neoplasm in the case described in this report, such a honeycomb appearance was not present because the neoplastic cells did not label with this marker. Thus, the neoplasm was not consistent with histiocytic sarcoma.

Although the histologic features were not consistent with hemangiosarcoma, occasionally more solid forms of this common splenic neoplasm can develop.3 Hence, to rule out the differential diagnosis of hemangiosarcoma, analyses for factor VIII-related antigen and CD31, which label endothelial cells, were performed. For the dog of this report, the endothelial cells of normal vessels had brown cytoplasmic labeling with each marker but the neoplastic cells were diffusely negative, thereby ruling out hemangiosarcoma (Figure 3). Although primary gastrointestinal stromal tumors (GISTs) have only been identified in the gastrointestinal tract of dogs,4,5 to further rule out GIST metastasis, immunolabeling for KIT was performed. This marker is commonly used to identify mast cell tumors, but labeling for this marker also defines a GIST.4,5 The neoplastic cells in the mass of the present report were not KIT positive, which ruled out a GIST. Because the neoplastic cells were negative for all of these more specific markers, labeling with a more generic marker, vimentin, was performed to confirm mesenchymal origin of the neoplasm. The neoplastic cells had red cytoplasmic labeling for vimentin, confirming their mesenchymal cell origin. On the basis of the results of the immunohistochemical analyses and the histologic features, the neoplasm in the dog of the present report was most consistent with an undifferentiated splenic sarcoma.

Splenic mesenchymal cell neoplasms are connective tissue tumors that frequently develop in many veterinary species.6 In dogs, these types of neoplasms are most commonly reported for large breeds such as the Golden Retriever, Labrador Retriever, Doberman Pinscher, and shepherd breeds.1,6 These neoplasms have a high rate of metastasis; in affected dogs, median survival time is approximately 1 year if treatment is not pursued.6 Biological behavior of splenic nonangiomatous, nonlymphatomatous neoplasms is closely associated with mitotic index, which has been shown to be the most useful morphologic prognostic factor. A mitotic index of 0 to 9 mitoses/10 hpf was associated with the longest survival times after splenectomy in 1 study1 of dogs with nonangiomatous, nonlymphomatous splenic neoplasms. In that study,1 a mitotic index of 10 to 30 mitoses/10 hpf was associated with survival times ranging from 1 to 2 months. The age of the dogs did not have a significant effect on survival time by tumor type because most dogs were 11 to 13 years old.1 In the case described in the present report, the mitotic index (4 mitoses/10 hpf) was not considered high, despite the extent of infiltration of the spleen and metastasis. Given the immunohistochemical findings and the histologic features, the neoplasm in the dog of this report was most likely an undifferentiated splenic sarcoma, which is classified as a nonangiomatous, nonlymphomatous splenic sarcoma.

References

  • 1. Spangler WL, Culbertson MR, Kass PH. Primary mesenchymal (nonangiomatous/nonlymphomatous) neoplasms occurring in the canine spleen: anatomic classification, immunohistochemistry, and mitotic activity correlated with patient survival. Vet Pathol 1994; 31: 3747.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2. Fulmer AK, Mauldin GE. Canine histiocytic neoplasia: an overview. Can Vet J 2007; 48: 10411043, 1046–1050.

  • 3. Göritz M, Müller K, Krastel D, et al. Canine splenic haemangiosarcoma: influence of metastases, chemotherapy and growth pattern on post-splenectomy survival and expression of angiogenic factors. J Comp Pathol 2013; 149: 3039.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Frost D, Lasota J, Miettinen M. Gastrointestinal stromal tumors and leiomyomas in the dog: a histopathologic, immunohistochemical, and molecular genetic study of 50 cases. Vet Pathol 2003; 40: 4254.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. Hayes S, Yuzbasiyan-Gurkan V, Gregory-Bryson E, et al. Classification of canine nonangiogenic, nonlymphogenic, gastrointestinal sarcomas based on microscopic, immunohistochemical, and molecular characteristics. Vet Pathol 2013; 50: 779788.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6. Baba AI, Câtoi C. Chapter 5. Mesenchymal tissue tumors. In: Comparative oncology. Bucharest, Romania: The Publishing House of the Romanian Academy, 2007:166.

    • Search Google Scholar
    • Export Citation
  • Figure 1—

    Photographs of the spleen and liver from a dog that was evaluated for chronic weight loss, anorexia, and vomiting. A—A large, expansile, multinodular, mottled tan to dark red mass is present in the body of the spleen. Bar = 5 cm. B—Notice the multifocal to coalescing, slightly raised, umbilicated, pale yellow masses in the liver. Bar = 5 cm. Inset—The masses extend into, efface, and partially compress the underlying hepatic parenchyma, which has an accentuated lobular pattern.

  • Figure 2—

    Photomicrograph of a section of the liver from the same dog in Figure 1. Neoplastic cells have infiltrated and extensively effaced the hepatic parenchyma. There is atrophy and dissociation of remaining hepatocytes entrapped within the neoplasm. H&E stain; bar = I mm. Inset—Higher magnification of the neoplastic spindloid cells, which infiltrate hepatic sinusoids. Anisocytosis and anisokaryosis are marked. H&E stain; bar = 200 μm.

  • Figure 3—

    Photomicrographs of sections of the neoplastic mass in the spleen of the dog in Figure 1. A—In the spleen, neoplastic cells are stellate to spindloid and arranged in dense bundles and sheets with a small amount of collagenous stroma. H&E stain; bar = 500 μm. B—Neoplastic cells (asterisk) are negative for CD 18. Notice the CD 18-positive brown perimembranous labeling of interstitial dendritic cells between the neoplastic cells. CD 18-specific stain with diaminobenzidine chromogen (brown); bar = 500 μm. C—Neoplastic cells are negative for CD31. Notice the CD31-positive brown perimembranous labeling of the endothelial cells lining vessels within the neoplasm. CD31-specific stain with diaminobenzidine chromogen (brown); bar = 50 μm. D—Neoplastic cells have strong red cytoplasmic labeling for vimentin. Vimentin-specific stain with amino-ethyl-carbazol chromogen (red); bar = 50 μm.

  • 1. Spangler WL, Culbertson MR, Kass PH. Primary mesenchymal (nonangiomatous/nonlymphomatous) neoplasms occurring in the canine spleen: anatomic classification, immunohistochemistry, and mitotic activity correlated with patient survival. Vet Pathol 1994; 31: 3747.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2. Fulmer AK, Mauldin GE. Canine histiocytic neoplasia: an overview. Can Vet J 2007; 48: 10411043, 1046–1050.

  • 3. Göritz M, Müller K, Krastel D, et al. Canine splenic haemangiosarcoma: influence of metastases, chemotherapy and growth pattern on post-splenectomy survival and expression of angiogenic factors. J Comp Pathol 2013; 149: 3039.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Frost D, Lasota J, Miettinen M. Gastrointestinal stromal tumors and leiomyomas in the dog: a histopathologic, immunohistochemical, and molecular genetic study of 50 cases. Vet Pathol 2003; 40: 4254.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. Hayes S, Yuzbasiyan-Gurkan V, Gregory-Bryson E, et al. Classification of canine nonangiogenic, nonlymphogenic, gastrointestinal sarcomas based on microscopic, immunohistochemical, and molecular characteristics. Vet Pathol 2013; 50: 779788.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6. Baba AI, Câtoi C. Chapter 5. Mesenchymal tissue tumors. In: Comparative oncology. Bucharest, Romania: The Publishing House of the Romanian Academy, 2007:166.

    • Search Google Scholar
    • Export Citation

Advertisement