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

## TL;DR

A cat was found to have a rare ectopic liver mass in its chest, highlighting the importance of recognizing this condition to avoid misdiagnosis.

## Contribution

This case study reports a rare instance of intrathoracic ectopic liver in a cat and emphasizes diagnostic challenges and clinical implications.

## Key findings

- Ectopic liver tissue was confirmed in a 6-year-old cat through cytologic and histopathologic analysis.
- The mass was congenital in origin and unrelated to trauma or diaphragmatic defects.
- Ectopic liver can mimic tumors, requiring awareness for accurate diagnosis and management.

## Abstract

The presence of liver tissue outside its normal anatomical location is defined as ectopic liver. In human medicine, it is an infrequent abnormality, and only a few cases have been reported in veterinary medicine. Ectopic liver is usually asymptomatic; however, previous studies have observed a higher risk of carcinogenesis in individuals with this condition, especially the development of hepatic carcinoma. This case study presents an incidental post-mortem finding of a large (9 cm) intrathoracic mass in a 6-year-old cat that died suddenly due to severe bacterial pneumonia. Cytologic and histopathologic examinations of the mass confirmed the presence of ectopic liver tissue. We briefly discuss the main findings in veterinary medicine regarding ectopic liver, including anatomical localization, reported species, mass sizes, histopathological features, and associated clinical symptoms. Although ectopic liver is rare, it can be easily misdiagnosed as a tumor mass, which may influence further clinical decisions. Therefore, it is important to increase awareness about this entity and improve clinical management.

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.