An Incidental Necropsy Finding: Intrathoracic Ectopic Liver in a Cat.

Ectopic liver is a rare anomaly characterized by the presence of hepatic tissue outside its normal anatomical location without continuity with the main liver. Reports of this condition are sporadic in human medicine, and cases in veterinary species remain limited. This condition may arise as a congenital developmental defect or as a consequence of prior traumatic injury leading to fragmentation and displacement of hepatic tissue. This case study describes an incidental intrathoracic ectopic liver identified in a 6-year-old male cat that died of acute suppurative bacterial pneumonia. Necropsy revealed a well-demarcated, encapsulated, large mass within the middle of the caudal mediastinum, unattached to the diaphragm, lungs, or pericardium. Cytologic and histopathologic examinations confirmed the presence of hepatic tissue with preserved lobular architecture. No evidence of previous trauma or diaphragmatic defects was present, supporting the congenital origin. The accompanying severe bacterial pneumonia was unrelated to the mediastinal mass. This study highlights the diagnostic challenges associated with intrathoracic ectopic liver, which can mimic neoplastic or inflammatory masses. Awareness of this entity is essential for accurate diagnosis. Given the documented risk of malignant transformation in ectopic hepatic tissue, surgical excision and histopathological assessment should be considered whenever such lesions are detected.