Abdominal imagingCase Type
Carolina Terra, Nuno Campos, Maria Antónia Portilha, Filipe Caseiro-Alves, Paulo DonatoPatient
71 years, female
A 71-years-old woman presented to our hospital with an abdominal ultrasound performed in an outside institution due to epigastric pain. The US scan revealed a non-specific complex focal liver lesion. Clinical observation was unremarkable. An abdominal CT was performed.
The CT study revealed a focal liver lesion in the right lobe. Figure 1 (a-c): The lesion was multilobulated, well-delineated, with areas of different densities. The most anterior part was composed by macroscopic fat, forming a fat-fluid level with the posterior portion displaying low cystic-like areas. A third and most posterior area showed intermediate density values (20-40 UH). The lesion did not enhance in the dynamic triphasic study after IV contrast administration.
Figure 2 (a,b): A coarse calcification was present within the lesion.
Figure 3: Hepatic veins were patent but deviated by the lesion without signs of invasion. There were no stigmata of chronic liver disease, ascites or peritoneal metastases. No abnormal lymph nodes were noted.
By definition, teratomas are derived from 2 or more germ cell layers: ectoderm, mesoderm, and endoderm.  The word itself is derived from the Greek word, teratos, meaning monster. They can contain different types of tissues such as adipose tissue, bony trabeculae, hair, fibrillary neural tissue and calcifications. Liver teratomas are very rare accounting for less than 1% of all teratomas.  The majority of liver teratomas are seen in children under 3 years of age, reflecting the origin from primordial germ cells, occurring extremely rarely in adults .
In adults, benign teratomas do not directly affect the general condition of the patient; they range from asymptomatic and incidentally found on CT scans to presenting with symptoms related to mass effect such as abdominal distension, fullness sensation, nausea and vomiting .
Ultrasound (US) of teratoma reveals hypo- or anechoic components representing its cystic parts along with hyperechoic foci denoting calcifications or macroscopic fat. A CT scan showing a well-circumscribed mass containing adipose tissue, fluid and calcifications is quite characteristic of the diagnosis  and the presence of fat-fluid levels are considered pathognomonic of teratoma.  Concerning the differential diagnosis of fat-containing liver masses it is quite vast and should include focal or geographic steatosis, adenoma, focal nodular hyperplasia, lipoma, angiomyolipoma, cystic teratoma, rare cases of hydatid cysts, hepatic adrenal rest tumour, pseudolipoma of the Glisson capsule, xanthomatous lesions in Langerhans cell histiocytosis and malignant lesions such as hepatocellular carcinoma, primary and metastatic liposarcoma . Teratomas can be categorised as benign or malignant on the basis of their histopathological features. The definitive diagnosis of mature teratoma is only possible by histologic examination. In the present case, the diagnosis remains presumptive since surgery was not performed so far.
Surgical resection is the mainstay of treatment since the presence of immature tissue of any germ layer adversely affects the prognosis. 
Take-Home Message / Teaching Points
The finding of a mass containing fat, fluid and calcification is virtually diagnostic of a teratoma, with the fat-fluid level being pathognomonic.
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