Clinical and Histopathological Features of a Thymolipoma in a Dog

Abstract

Abstract. This study presents a case of a canine thymolipoma, which is a rare, slow-growing, benign tumor of the thymus composed of mature adipose tissue and thymic tissue. A 9-year-old spayed, female miniature pinscher presented with chronic cough and dyspnoea. Radiology revealed pleural effusion and a mediastinal mass with a fatty appearance. The mass was attached to, and silhouetted, the adjacent pericardium. Microscopically, the mass was composed of adipose tissue with numerous cords and nests of thymic tissue without corticomedullary arrangement. To the authors' knowledge, this is the first description of this uncommon neoplasm in a dog. The gross and histological findings are similar to those described for thymolipomas in humans. The possible histogenesis for this neoplasia in a dog is also discussed.

Canine Epithelial Thymic Tumors: Outcome in 28 Dogs Treated by Surgery

“…In fact, two main issues are present when differentiating thymomas from other mediastinal masses: the macroscopic differentiation by imaging from space-occupying masses, and microscopic differentiation from lymphoma before histology of the resected mass is performed. The differential diagnosis should be primarily versus mediastinal lymphoma, but other space-occupying masses should also be ruled out, such as branchial cysts, ectopic thyroid or parathyroid tumors, chemodectoma, thymic cysts, metastatic neoplasia, abscesses, granulomas, and other rarer thymus disorders such as thymolipoma and thymofibrolipoma [18][19][20][21]. MG was not resolved in two cases but was managed with lifelong pyridostigmine administration; hypercalcemia was resolved after surgery but recurred in the dog with thymic carcinoma at the time of tumor recurrence.…”

Thymofibrolipoma in a Labrador Retriever

“…5 Thymolipomas, which are characterized by abundant adipose with a minor component of interspersed thymic tissue, have been reported in 1 male domestic shorthair cat and 1 spayed female miniature pinscher. 8,10 A clear distinction is not evident between a thymofibrolipoma and a thymic lipofibroadenoma. The latter was first described by Kuo et al in reporting a mass arising from an adjacent thymoma.…”

Canine Lipomas Treated with Steroid Injections: Clinical Findings

“…They have occasionally been described within the thorax and the abdomen, causing clinical signs associated with organ compression [6]–[8]. The occurrence of a thymolipoma has been reported in one dog [9] and of thymofibrolipomas in two dogs [10]. Infiltrative lipomas have also been recognised in dogs, appearing histologically as benign adipocytes invading the muscle, the fascia, and occasionally the bone [11]–[14].…”