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A 2-year-old, intact male Newfoundland was presented for evaluation of a 1- to 2-day history of coughing, retching, and progressive lethargy. Thoracic radiographs demonstrated right-sided pleural effusion and lobar vesicular emphysema. An exploratory thoracotomy revealed midlobar torsion of the right caudal lung lobe. A partial lung lobectomy was performed, and following surgery, the dog recovered without complications. Lung lobe torsions in dogs typically occur at the hilus of the affected lung lobe. This report documents that midlobar lung lobe torsions occur in dogs and should be considered as a differential diagnosis in cases of lobar vesicular emphysema and pleural effusion.

Objective: To determine the estrogen receptor (ER) content of canine mammary gland tumors by use of immunohistochemical (IHC) examination of formalin-fixed sections., Sample Population: 21 mammary gland tumors from 20 adult dogs., Procedure: ER were detected in formalin-fixed tissues, using an avidin-biotin alkaline phosphatase IHC assay and were quantified on fresh-frozen tumor samples, using a modified dextran-coated charcoal (DCC) assay., Results: 7 of 21 tumors had visually detectable nuclear ER by use of IHC staining, whereas 8 of 21 tumors were positive for ER by use of the DCC assay. The ER-positive cells in 5 IHC-positive tumors were epithelial cells with histologic criteria of early malignancy. The remaining 2 ER-positive tumors detected by use of IHC had ER-positive mast cells within areas of connective tissue around the tumor., Conclusions: Immunohistochemistry is an additional method for detection of ER in canine mammary tumors. The major advantage of this type of assay is that it may be performed on formalin-fixed tissues, and individual ER-positive cells may be identified. Discovery of ER-positive mast cells by use of IHC is of concern, particularly if the ER status of a tumor is based on DCC results alone., Clinical Relevance: Because most canine mammary tumors are fixed in formalin prior to histologic evaluation, an IHC assay that identifies ER-positive cells is desirable. Adjunctive antiestrogen therapy could be administered to dogs with ER-positive tumors.

Long-term follow-up information was obtained for 39 dogs that had undergone surgical excision of nonlymphomatous, small intestinal tumors. For all dogs evaluated in this study, the median survival time was 10 months, and the one- and two-year survival rates were 40.5% and 33.1%, respectively. There was no difference in survival times between dogs with adenocarcinomas (n=23) and dogs with leiomyosarcomas (n=16). Survival times were significantly (p less than 0.0001) shorter for dogs with histological evidence of metastases at the time of surgery (median, 3.0 months) than for dogs with no histiological evidence of metastases (median, 15.0 months).

Objective: To characterize the frequency, clinical signs, biologic behavior, and response to treatment of tumors of the ear canal in dogs and cats., Design: Retrospective analysis of medical records., Animals: Medical records of 81 dogs (48 malignant tumors, 33 benign tumors) and 64 cats (56 malignant tumors, 8 benign tumors)., Procedure: Data were analyzed for cats and dogs with malignant tumors, and risk factors were analyzed for their potential impact on survival time., Results: Malignant tumor types most commonly reported included ceruminous gland adenocarcinoma, squamous cell carcinoma, and carcinoma of undetermined origin. Median survival time of dogs with malignant aural tumors was > 58 months, whereas that of cats was 11.7 months. A poor prognosis was indicated by extensive tumor involvement (dogs) and by neurologic signs at time of diagnosis, diagnosis of squamous cell carcinoma or carcinoma of undetermined origin, and invasion into lymphatics or blood vessels (cats)., Clinical Implications: Malignant tumors of the ear canal in dogs and cats have a propensity for local invasion, but tend not to metastasize. Squamous cell carcinoma and carcinoma of undetermined origin were the most locally aggressive tumors. Malignant tumors of the ear canal are best managed by aggressive surgical excision. Radiotherapy may be useful when tumors cannot be completely removed.

Medical records of 36 dogs with synovial sarcoma confirmed by microscopic examination of H&E-stained sections of tissue were selected for retrospective analysis from dogs admitted between 1986 and 1991 to participating institutions of the Veterinary Cooperative Oncology Group. Metastasis was evident at the time of diagnosis in 8 (22%) dogs, and 15 (41%) dogs ultimately developed metastatic tumors. Median survival time for all dogs, as determined by life-table analysis, was 17 months. For dogs that were subsequently treated and became tumor free, the median disease-free interval was 30 months. Nine dogs had previously had localized excision attempted, but all had recurrence of the tumor locally (median, 4.5 months). Of 29 dogs that underwent amputation, including the 9 with localized recurrence, 2 had tumor recurrence on the amputation stump. Most dogs had survival time and disease-free interval of > 36 months after amputation. Four dogs that had received chemotherapy for tumors of advanced clinical stages did not respond to treatment. One dog that had received locally applied radiotherapy after localized excision did not have evidence of tumor recurrence 2 years after radiotherapy. Clinical stage, histologic grade, and a positive result for tests that used cytokeratin immunohistochemical staining significantly (P < 0.05) influenced survival time and disease-free interval. Analysis of data for the study reported here suggested that histologic criteria can be an excellent predictor of dogs that are likely to have tumor recurrence after amputation and that would most likely benefit from aggressive treatment with adjuvants.

An inexpensive combination chemotherapy protocol containing cyclophosphamide, dactinomycin, and 5-fluorouracil was evaluated in dogs with carcinomas. Fifteen dogs were entered in this study, and there were 1 complete response and 2 partial responses among 12 evaluable dogs. However, 6 of 15 dogs (40%) developed neurotoxicity. The neurotoxicity of this protocol was compared with a previous 5-fluorouracil-containing protocol and found to be significantly higher. Due to the unacceptably high rate of neurotoxicity, this protocol cannot be recommended for use in dogs with cancer.

Mast cell tumors (MCTs) are common in the dog, occurring most frequently in the skin and subcutaneous tissues. Their biologic behavior can be quite variable, with approximately 50% being malignant. Although clinical features and histologic grading can help determine the likelihood of malignancy, it is difficult to predict the biologic behavior of an individual tumor. Consequently, all MCTs should be considered potentially malignant. Wide surgical excision is the most common therapy for canine MCTs, although approximately 50% recur locally. Nonresectable or recurrent MCTs can be treated with radiation and/or chemotherapy. Chemotherapy is also used in the treatment of metastatic MCTs, and it may be helpful in preventing the recurrence and/or metastasis of undifferentiated tumors.

Subclinical abnormalities in hemostasis occur commonly in small animal patients with cancer, but the incidence of clinical thrombosis or hemorrhage is unknown. Malignancy can lead to abnormalities in both primary and secondary hemostasis, which in turn can lead to either thrombotic or hemorrhagic tendencies. These coagulation abnormalities can be associated with the tumor itself, with anticancer chemotherapy, or with secondary organ dysfunction. Thrombocytopenia and DIC are probably the most common defects associated with clinical bleeding in small animal patients.

The clinical and pathologic features of systemic mastocytosis in 16 dogs are reported. There was no apparent breed or sex predilection, and the median age at presentation was 9.5 years. In 14 of 16 cases there was a primary cutaneous mast cell tumor (MCT). When cutaneous tumor location was compared with previous reports, there was no association between location and systemic dissemination. The most common presenting signs associated with the cutaneous tumor were regional dissemination, edema, ulceration, and abscessation. They were present in 12 dogs (69%). Signs of systemic illness, including anorexia, vomiting, and diarrhea, were seen in eight dogs (50%). Other than the cutaneous tumors, the most consistent physical and radiographic abnormalities included lymphadenopathy, splenomegaly, and hepatomegaly. Eosinophilia and basophilia were seen in two and five dogs, respectively. Six dogs had increased numbers of mast cells in peripheral blood or buffy coat smears. Five of the nine dogs evaluated had increased numbers of mast cells in bone marrow aspirates. Bone marrow aspiration was superior to both peripheral blood and buffy coat smears in predicting mastocytosis. Coagulation abnormalities were seen in three of five dogs tested. Using a conventional histomorphologic grading system, 10 of 13 (77%) tumors were classified as Grade III or undifferentiated and were overrepresented when compared with previous reports of cutaneous MCTs. Eighty-eight percent of the dogs either died or were euthanatized because of their tumors. Organs commonly involved at necropsy included lymph nodes, spleen, liver, and bone marrow; four dogs had gastroduodenal ulcers.

Results from transabdominal fine-needle aspiration of the spleen in 28 dogs and 5 cats are reported. Splenomegaly was present in 79% of these patients, and splenic masses were present in 15%. Extramedullary hematopoiesis, the most common cytologic diagnosis, was found in 24% of the patients and was associated with a variety of diseases including immune hemolytic anemia, hemangiosarcoma, and bone marrow hypoplasia. Hematopoietic neoplasms including lymphosarcoma, plasmacytoma, myelogenous leukemia, and systemic mastocytosis were diagnosed in 24% of the patients. Other diagnoses included malignant neoplasia of undetermined cell type and lymphoreticular hyperplasia. Splenic aspirates were considered normal in 18% of the animals. Two (6%) of the aspirates contained liver tissue rather than spleen. Histologic evaluation of splenic tissue was performed in 42.5% of the patients. All cytologic diagnoses correlated well with their final histologic diagnoses. Complications from the aspiration procedure were not observed, even in thrombocytopenic patients.