Procedure: Ultrasound-guided biopsy of left hepatic lobe nodule.

Diagnosis: Liver involvement by a poorly differentiated adenocarcinoma.

Immunohistochemistry shows strong positivity of the tumor cells with antibody pancytokeratin (AE1/AE3, CK7 and CK19). The tumor is negative for HMB45, PS100, CK20 and antihepatocytes. The immunostain with antibody CDX2 is focal.  This phenotype is suggestive of pancreaticobiliary origin; however, if the tumor is primary in the liver, the diagnosis of intrahepatic cholangiocarcinoma, poorly differentiated should be considered. 

Further immunohistochemical study was performed and show positivity of the tumor cells by the antibodies anti-CA 125, anti-TTF-1, anti-CEA and anti-galectin-3, however, these tumor cells do not express PSA, AMACR, CA 19.9, CD10, thyroglobulin and calcitonin.  The anti-TTF-1 positivity is usually seen in lung and thyroid, however, some rare cases of cholangiocarcinoma can also be positive.

The patient had a nodule in the left thyroid lobe on ultrasound examination (low-suspicion for malignancy according to the ATA-2015 guidelines). FNAC of this thyroid nodule was done which was negative for malignancy. No other suspicious abnormality was seen on the whole-body CT scan, particularly in the lungs, to suggest the primary source.