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S. Ettinger1
Splenic tumors
Sue Ettinger, DVM, DACVIM (Oncology)
Dr Sue Cancer Vet PLLC and Animal Specialty & Emergency Center Wappinger Falls, NY, USA Key Points
• Dogs with splenomegaly and splenic masses generally follow the “double two-thirds rule”: 2/3 have splenic neoplasia, and 2/3 of those have hemangiosarcoma. So 1/3 do not have cancer! Hemangiosarcoma is not the only differential for a dog with a splenic mass.
• is the most common primary canine splenic cancer in dogs, and it is locally aggressive and highly metastatic.
• The likelihood of splenic tumor increases with anemia, nucleated RBC, abnormal RBC morphology, or splenic rupture.
• Prognosis for splenic masses cannot be determined without histology which usually requires surgery. A common clinical error is to assume HSA based on the presence of a splenic mass. Large masses are not necessarily malignant. Several splenic lesions have similar ultrasound and gross appearances.
• Except for lymphoma, splenectomy is the treatment of choice for splenic tumors when there is no evidence of metastasis based on staging tests. Even at surgery, it is often impossible to distinguish various diseases based on gross appearance of the spleen or liver.
• Dogs with HSA treated with local therapy and chemotherapy live longer than dogs without treatment and with local therapy only but 1-year survival rates are still low (10%). Chemotherapy is generally well- tolerated in most dogs, and only a minority develops significant toxicity.
Who, What, Where, Why
Splenic neoplasia can arise from any of the normal splenic tissues including blood vessels, lymphoid tissue, smooth muscle and connective tissues. Common splenic tumors include HSA, mast cell tumor, lymphoma and various sarcomas. Hematomas are the most common benign splenic masses. Splenic tumors usually occur
in large breed dogs. Breeds most at risk are German
shepherd dog, golden Retrievers, and Labradors. German shepherds also have a high prevalence of hyperplastic nodules and hematoma.
Clinical signs are typically vague, non-specific and include enlarged abdomen, anorexia, lethargy, depression, vomiting, and diarrhea. Clinical signs also vary with how advanced disease is, so dogs may have acute and often dramatic acute signs including collapse and hypovolemic shock. In one study 80% of dogs with acute abdomen and no history of trauma had malignant cancer and 88% were HSA. Splenomegaly is readily detectable through abdominal palpation, radiography and ultrasonography.
Differentials Diagnoses: Hemangiosarcaoma is not the only differential for a dog with a splenic mass. A common clinical error is to assume HSA based on the presence
of a splenic mass. Large masses are not necessarily malignant. Several splenic lesions including HSA, hemangioma and hematoma have similar ultrasound and gross appearances.
Lymphoma (LSA): LSA that involves the spleen is most commonly part of multicentric LSA and typically is a diffusely infiltrative disorder. Some lymphomas may occur as solitary splenic nodules, especially marginal zone lymphoma and mantle subtypes of the indolent form. Similarly acute and chronic leukemias can also diffusely infiltrate the spleen.
Malignant Histiocytosis (MH): MH is an uncommon cancer of atypical histiocytes and has progressive, multicentric involvement of multiple organs, including the spleen, liver, lymph nodes, and bone marrow. The Bernese mountain dog has a familial predilection.
Mast Cell tumors (MCT): Tumors of primary visceral organs including the spleen are rare in dogs. Visceral mastocytosis is typically preceded by a poorly differentiated cutaneous MCT.
Splenic sarcoma: Splenic sarcomas are non- angiomatous, non-lymphoid tumors of connective tissues and include fibrosarcoma, leiomyosarcoma, extraskeletal osteosarcoma, and undifferentiated sarcomas. A high mitotic index (MI) of >9 is a negative prognostic factor for survival. Splenic sarcomas tend to be fatal within 1 year. Splenic leiomyosarcoma have a high metastatic rate but dogs that survive the initial post-surgical period have a MST of 8 months.
Hemangioma Hemangiomas are benign tumors of blood vessels. Surgery is curative,
Non-neoplastic: hematoma, abscess, nodular hyperplasia, granuloma
An Urban Experience

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