Mediastinal Lymphoma in a Bitch: Clinical Management of Thrombotic Complications

Abstract

Background: The association between neoplasia and hypercoagulability has received increasing recognition, and lymphoma is one of the neoplastic diseases associated with thromboembolic complications. In human medicine, reduced mobility, tumor location, and chemotherapeutic agents are recognized as established risk factors for thrombosis. This report describes one bitch with T-cell mediastinal lymphoma complicated by pulmonary thromboembolism (PTE) and iliac vein thrombosis,
emphasizing the importance of recognizing thrombosis-related risk factors in canine lymphoma.
Case: A 10-year-old spayed bitch Tosa was presented with vomiting, diarrhea, and anorexia. Computed tomography (CT) revealed a cranial mediastinal mass. Fine-needle aspiration cytology and polymerase chain reaction for antigen receptor rearrangement confirmed a diagnosis of high-grade T-cell mediastinal lymphoma. Prednisolone monotherapy was initiated. Three months later, the patient was re-presented with respiratory distress and right hindlimb swelling. Thromboelastography (TEG) showed hypercoagulability. Portable glucose and lactate measurements revealed decreased glucose and increased lactate in the right hindlimb relative to the left, suggesting an ischemic condition. Thoracic radiographs demonstrated a moderate volume of pleural effusion. CT revealed concurrent PTE and right iliac vein thrombosis, along with enlargement of the mediastinal mass and regional lymph nodes compressing the cranial vena cava. Treatment with L-asparaginase and lomustine was initiated, and antithrombotic agents including clopidogrel and rivaroxaban were concurrently administered. Three weeks after the treatment initiation, blood glucose levels and lactate concentrations in right hindlimb returned to normal levels. TEG showed an improvement in hypercoagulability. Thoracic radiographs showed resolution of pleural effusion. These findings indicated that thrombotic complications were successfully controlled. However, the patient died 4 months after initial diagnosis of mediastinal lymphoma.
Discussion: This report describes a case of pulmonary thromboembolism and iliac vein thrombosis in a bitch with mediastinal lymphoma, suggesting potential risk factors that may have contributed to thrombogenesis. Mediastinal lymphoma, as demonstrated in this animal, can mechanically compress major vessels such as the cranial vena cava, predisposing to venous stasis and thrombus formation. This mechanism is consistent with observations in human medicine, where vascular compression by mediastinal tumors markedly increases thrombotic risk. Chemotherapeutic agents such as glucocorticoids and L-asparaginase are known to decrease antithrombin synthesis and enhance platelet activity, thereby amplifying thrombotic potential in patients already predisposed by neoplasia. Furthermore, reduced mobility related to lethargy or hospitalization can intensify venous stasis, a mechanism well established in human oncology. These interacting factors likely acted synergistically in this patient to promote thrombus formation. TEG proved valuable for monitoring dynamic coagulation changes, sensitively reflecting both the hypercoagulable state and subsequent improvement with treatment. Incorporating such monitoring may help clinicians detect early coagulation imbalance and evaluate therapeutic response in real time. Overall, this case highlights that in canine lymphoma, vascular compression within the mediastinal space, the use of chemotherapeutic agents, and patient immobility can collectively increase the risk of thrombosis. Recognizing these concurrent risk factors is crucial for timely intervention. TEG-based monitoring and early intervention may improve clinical outcomes in dogs with mediastinal lymphoma.

Keywords: dog, canine, haematopoietic neoplasia, mediastinal lymphoma, thromboelastography, thromboembolism.