Metastatic carcinoma of unknown origin in a dog.

Although cancer of unknown primary origin (CUP) is well-described in the human literature, it is not as well-understood within veterinary medicine. This case report represents one of few focused on describing CUP in a dog. Key clinical message: Metastatic CUP should be considered as a differential diagnosis despite being a rare disease entity that is infrequently reported within the veterinary literature.

Carcinome métastatique d'origine inconnue chez un chien. Bien que le cancer d'origine primaire inconnue (CUP) soit bien décrit dans la littérature humaine, il n'est pas aussi bien compris en médecine vétérinaire. Ce rapport de cas représente l'un des rares à s'intéresser à la description du CUP chez un chien.Message clinique clé:Le CUP métastatique doit être considéré comme un diagnostic différentiel bien qu'il s'agisse d'une entité de maladie rare rarement rapportée dans la littérature vétérinaire.(Traduit par Dr Serge Messier).

Cancer of unknown primary in a mare: case report and comparative pathology review.

A 25-y-old Percheron mare was admitted to the teaching hospital because of lethargy and intractable dyspnea. Thoracoabdominal ultrasound examination identified severe peritoneal effusion, mild bilateral pleural effusion, and a diffuse pulmonary nodular pattern. Cytology of peritoneal fluid revealed a hypercellular sample with clusters of neoplastic polygonal cells and admixed macrophages. Euthanasia was followed by postmortem examination; marked bi-cavitary effusion was present, and innumerable up to 4-cm diameter, round-to-floriform nodules were diffusely evident throughout serosal surfaces as well as the pulmonary and hepatic parenchyma. Disseminated adenocarcinoma, predominantly affecting lung and liver with widespread serosal implantation, was confirmed on light microscopy. Neoplastic cells had strong immunolabeling for pancytokeratin and lacked immunoreactivity to vimentin, napsin A, and Pax8. Cytokeratin 7 and thyroid transcription factor-1 were non-contributory given absent and inconsistent internal control reactivity, respectively. Such results, combined with the lack of a major mass that would indicate a primary site, were supportive of carcinoma of unknown primary site, which remains a conundrum in human oncology, and is poorly explored in veterinary medicine, mainly as a result of clinical and diagnostic limitations.

Squamous cell carcinoma of unknown primary origin in a dog presenting with bone metastasis.

A 10-year-old female American Pit Bull dog was diagnosed with metastatic undifferentiated carcinoma of the scapula. Immunohistochemistry showed positive immunoexpression for cytokeratins (AE1/AE3, 34BE12, CK7) and vimentin, confirming squamous cell carcinoma. No evidence of nodules was found in the complete physical examination and imaging procedures conducted. The patient was diagnosed with carcinoma of unknown primary origin. Amputation and adjuvant chemotherapy with doxorubicin and piroxicam were performed, but the patient died of respiratory failure after 737 days of diagnosis. Necropsy confirmed undifferentiated carcinoma infiltrating the lungs and kidneys, and showing the same immunoexpression as the tumor in the scapula. Amputation associated with chemotherapy extended the overall survival time of this patient.

Metastatic cancer of unknown primary in 21 dogs.

The aim of this retrospective study was to describe clinical features, treatment and outcome of 21 dogs with metastatic cancer of unknown primary (MCUP), a biopsy-proven malignancy being diagnosed at a metastatic stage, in which the anatomical origin of the primary tumour cannot be detected. All dogs underwent total-body computed tomography. Signalment, type and duration of clinical signs, metastasis site, pathology results, treatment and outcome were recorded. Carcinoma was the most common diagnosis (57.1%), followed by sarcoma, melanoma and mast cell tumour. The median number of disease sites per dog was 2, with bones, lymph nodes, lungs and spleen being the most frequent metastatic locations. The median survival for all dogs was 30 days. Overall, a primary site was not identified in 20 (95.2%) dogs. MCUP encompasses a variety of different pathologic entities and harbours a poor prognosis.

Thoracic high-resolution computed tomography in the diagnosis of metastatic carcinoma.

Three dogs were presented for investigation of recurrent pyrexia of unknown origin, chronic vomiting and respiratory distress, respectively. One dog was markedly underweight and the other two were cachexic. Physical examination and initial diagnostic tests failed to establish the underlying cause of the presenting signs. Thoracic radiographs were within normal limits for the age of the dog. In each case there was a high index of suspicion for an occult neoplastic process in view of the profound unexplained weight loss present. High-resolution computed tomography (HRCT) of the thorax was performed. The lung fields were divided into three zones for analysis and a novel classification scheme was used to describe the HRCT findings in each zone. Postmortem examination and histopathology confirmed the presence of an infiltrating metastatic carcinoma in all three cases. The HRCT changes correlated closely with the pathological findings. The authors conclude that HRCT of the lung should be considered for pulmonary metastatic screening in the dog and introduce a classification system for HRCT findings, based on terminology used in human medicine.

Pericardial effusion associated with metastatic disease from an unknown primary tumor in a dog.

A 6.5-year-old, spayed female Siberian husky presented with signs of cardiac tamponade and weakness. Pleural, pericardial, and abdominal effusion were identified with radiographs and ultrasound. Pericardiocentesis relieved signs of tamponade, and the dog was clinically improved. Pericardial effusion recurred, and pericardiectomy was performed. Histopathological examination of excised tissues failed to reveal evidence of infectious or neoplastic disease. After pericardiectomy, clinically apparent thoracic effusion persisted. The dog was euthanized, and postmortem histopathological examination revealed emboli of metastatic carcinoma cells in the epicardium. The location of intrathoracic disease in this dog made antemortem diagnosis difficult, if not impossible.

Thrombosis of the caudal vena cava presenting as an unusual cause of an abdominal mass and thrombocytopenia in a dog.

Thrombosis of the caudal vena cava in a dog secondary to metastatic neoplasia is described. The dog had a palpable abdominal mass and persistent thrombocytopenia due to a thrombosed caudal vena cava that was surgically removed. A few days after its removal, the dog died and neoplastic cells of neural crest origin were identified at the edge of the thrombus. Massive thrombosis can be an unusual cause of platelet consumption, leading to thrombocytopenia and disseminated intravascular coagulation. Deep vein thrombosis of the vena cava can occur in dogs and may mimic an abdominal mass. Multiple mechanisms may be involved in the development of venous thrombosis, including endothelial damage by neoplastic cells and the presence of a hypercoagulable state secondary to neoplasia. Extensive collateral circulation may allow removal of diseased vena cava.

Malignant hypomelanotic melanoma of mules. A histologic, immunohistochemical and ultrastructural study of a case with unknown primary site and widespread metastases.

An unusual case of malignant hypomelanotic melanoma occurred in a 15-year-old gray mantle mule with unknown primary site and widespread metastatic growth is described. An ante-mortem examination, the presence of subcutaneous nodules was noted; histologically they are constituted by spindle or polygonal-shaped tumour cells with rare black granules in the cytoplasm; the immunohistochemical procedures showed a large expression of S-100, vimentin and HMB-45 antibodies, suggesting thus a diagnosis of malignant melanoma. Ultrastructural findings, obtained on formalin-fixed paraffin-embedded material, showed characteristic melanosomes and irregular fibrillary centers in nuclei of neoplastic cells. At post-mortem examination, other nodular mostly melanotic lesions were appreciable in lungs, kidneys, brain, liver, pancreas, spleen, lymph nodes and muscles. The importance of immunohistochemical and ultrastructural findings for the differential diagnosis of this neoplasm is emphasized.