Intrathoracic Accessory Lobe of the Liver

Clinical History: A 20-year-old woman presented to the physician with a rectal mass that was malignant on biopsy. Chest radiograph and abdominal CT were ordered to look for metastases.

Figure 1: Chest radiograph (PA view) showing a lobulated mass obliterating the right costophrenic angle and the diaphragm.

Figure 2:
Coronal maximum intensity projection computed tomography image shows the lesion to be lobulated, isodense to liver and getting supply from right posterior branch of the portal vein (arrow). 

Findings:

Her chest radiograph (postero-anterior view) shows a lobulated mass obliterating the right costophrenic angle and the diaphragm (Figure 1). Coronal maximum intensity reformatted CT image (Figure 2) shows the lesion to be lobulated, isodense to liver and getting supply from right posterior branch of the portal vein. The orthotopic liver was normal in configuration. Biopsy from the mass was done which showed normal liver tissue.

Diagnosis: Intrathoracic accessory lobe of the liver

Discussion: If the tissue is in communication with the main liver, it is termed as an accessory lobe, and it is termed ectopic if there is no communication [1]. Intrathoracic accessory lobe of the liver shows attenuation and morphology similar to that of normal orthotopic liver. As the development of both liver and diaphragm are closely related, this anomaly could be due to persistence of the pleuro-peritoneal canal [2].

References:
1. Collan Y, Hakkiluoto A, Hastbacka J: Ectopic Liver. Ann Chir Gynaecol 1978; 67: 27-29.
2. Roux BT. Heterotopic intrathoracic liver. Thorax 1961; 16: 68.

Shivali V Kashikar, MD, associate professor, Department of Radiodiagnosis, Jawaharlal Nehru Medical College, India; and Amol Gulkari, MD, consultant radiologist