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The aim of this study was to document the molecular clonality of lymphoid cells in canine thymoma using polymerase chain reaction for antigen receptor rearrangement (PARR). Fifteen formalin-fixed and paraffin wax-embedded samples of canine thymoma were analyzed for T- and B-cell receptor clonality. Two of these 15 cases were excluded from the study due to insufficient DNA concentration. Twelve of the 13 remaining samples (92.3%) showed a polyclonal lymphoid component and in one case the lymphoid component was monoclonal (T-cell clonality). PARR could therefore be a useful tool for differentiating canine thymoma from canine mediastinal lymphoma., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

An 11-year-old female Chihuahua exhibited respiratory distress and a computed tomography scan showed a large mass in the anterior thoracic cavity. During surgery, it was found that the mass was strongly adherent to surrounding tissue. A histopathological examination of a biopsy sample from the mass revealed proliferation of atypical epithelial cells and cartilage formation admixed with mature lymphocytes. Immunohistochemically, the tumour cells, as well as the normal canine thymic epithelial cells, were positive for pan-cytokeratin (CK), CK5/6, CK19, p63 and bone morphogenetic protein (BMP) 6. Foci of cartilage tissue were formed in association with the neoplastic epithelial tissue. In the normal canine thymus, the subcapsular epithelial cells are positive for both CK19 and BMP6. These findings indicate that the cartilage element within the tumour developed from CK19-positive neoplastic epithelial cells, which were derived from the thymic subcapsular epithelium. This case represents a novel variant of canine thymic epithelial tumour that exhibits cartilage differentiation., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

A 10-year-old captive male Siberian tiger (Panthera tigris altaica) presented with acute onset collapse, vomiting and dyspnoea, preceded by a 6-month period of progressive muscle wasting. Following humane destruction, post-mortem examination revealed a large multilobulated mass in the cranial mediastinum, which was diagnosed as a T-lymphocyte-rich thymoma with the aid of immunohistochemistry. Retrospective serology for acetylcholine receptor antibodies (titre 3.90 nmol/l) confirmed a diagnosis of thymoma-associated myasthenia gravis. Thymomas are reported rarely in wild carnivores, but when detected they appear to be similar in morphology to those seen in domestic carnivores and may also be accompanied by paraneoplastic syndromes. The clinical signs of myasthenia gravis in the tiger were consistent with those reported in cats and dogs and the condition is proposed as an important differential diagnosis for generalized weakness in captive Felidae., (Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Unlabelled: HISTORY AND PRESENTATION: A 12 year old, 4.2 kg, domestic long hair, castrated male cat was presented with regurgitation, inability to retract the claws, general weakness, cervical ventroflexion and weight loss. A thymic mass was evident on radiographs. Acetylcholine receptor antibody titer was positive for acquired myasthenia gravis (MG). Thymectomy via midline sternotomy was scheduled. ANESTHETIC MANAGEMENT:  Oxymorphone and atropine were administered subcutaneously as premedication, and anesthesia was induced with etomidate and diazepam given intravenously to effect. The cat's trachea was intubated and anesthesia was maintained with isoflurane in oxygen, and continuous infusions of remifentanil and ketamine. Epidural analgesia with preservative-free morphine was administered prior to surgery. Postoperative analgesia was provided by oxymorphone subcutaneously, interpleural bupivacaine, and fentanyl infusion. Postoperative complications included airway obstruction, hypoxemia and hypercapnia., Follow-Up: The cat was discharged 3 days after surgery. Discharge medications included pyridostigmine and prednisone. Nine days after surgery, the cat had a significant increase in its activity level, and medications were discontinued. Histopathologically, the mass was consistent with a thymoma. Approximately 6 weeks later the cat became weak again and pyridostigmine and prednisone administration was resumed., Conclusion: The perioperative management of patients with MG for transsternal thymectomy is a complex task. The increased potential for respiratory compromise requires the anesthesiologist to be familiar with the underlying disease state, and the interaction of anesthetic and non-anesthetic drugs with MG. Careful monitoring of ventilation and oxygenation is indicated postoperatively., (© 2011 The Authors. Veterinary Anaesthesia and Analgesia. © 2011 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.)

Thymolipomas are unusual benign neoplasms composed of mature adipose and thymic tissue that represent less than 10% of all thymic tumours in man. A thymofibrolipoma is a histological variant of thymolipoma in which there is an additional abundance of fibrous connective tissue. Thymolipoma has been reported previously in one dog and one cat, but thymofibrolipoma has never been described. This report documents the clinical and pathological features of two cases of canine thymofibrolipoma.

A cystic mass in the anterior mediastinum of a 9-year-old female European Shorthair cat was classified as a lymphocytic thymoma based on its histopathological features which were in accordance with those reported in the literature concerning feline thymomas. The application of a polyclonal keratin antiserum and monoclonal keratin antisera RCK 102, RKSE 60 and RGE 53 resulted in staining of foetal feline thymic cells, oesophageal epithelial cells as well as numerous stellate tumour cells and Hassall's corpuscles. As a result, the epithelial origin of the neoplastic cells could be established and the classification of thymoma confirmed. The results indicate the value of keratin antisera in the differentiation of thymoma and non-epithelial tumours in the anterior mediastinum.

A case of swine thymic lymphoma is described. A young pig had a mediastinal mass and bone marrow involvement and the microscopic findings showed peripheral blood involvement. The tumour was composed of small to medium sized lymphoid cells which formed rosettes with sheep erythrocytes and were characterized by narrow cytoplasmic bands, nuclear convolution and clustered dense bodies. Such structural and immunological features resembled those of human thymic lymphomas derived from thymic T-cells.

The features of 192 primary thymic tumours occurring in the rat are described. Of these neoplasms, 170 were classified as benign thymomas, one as a benign fibrous histiocytoma, 20 as various types of malignant thymoma, 3 lympho-epithelioma-like carcinomas, one mixed small cell undifferentiated-squamous cell carcinoma, one sarcoma-like carcinoma, 4 undifferentiated carcinomas, 11 squamous cell carcinomas and the one remaining tumour as a carcinoid. A mouse, anti-epithelial, monoclonal antibody, lu-5, was used to confirm the epithelial nature of the malignant thymomas, and neuron-specific enolase to confirm the diagnosis of carcinoid. The tumours showed many features in common with those reported in man.

A malignant spindle cell thymoma in a 14-year-old cat is described. The tumour showed mucoid differentiation and multiple lung metastases.