I had a liver lesion found on ultrasound, they found it as I had pneumonia that wouldnt go so they did blood tests and found my liver bloodwork was elevated with an 'infection'. I then had a ct, mri & endoscope, I found out 2 weeks later it was an 'undetermined lesion'. But they have decided it's not cancer&the lesion caused by the 'infection", the infection may have been caused by a condition called PBC, Primary Billiary Cholongitis  which I have been diagnosed as having. I will require medication for life for this, which will hopefully control the condition. 

So your partners lesion, could be a cyst, or ulcer or another liver disorder, like in my case.