According to Bild, the ex-Germany international had a growth discovered on his body during an MRI examination by doctors. He immediately underwent surgery in Hanover to remove the tumour from near his spinal cord during the lockdown.
Laboratory examinations recently cleared Ballack of any fears that the growth was cancerous, with results showing the tumour was benign.
The 43-year-old is said to be recovering on holiday in Portugal, where he is watching his former team Bayern Munich in the Champions League.
Ballack who hung up his boots eight years ago, earned 98 caps for his country and inspired them to the final of the World Cup in 2002.
He spent four years at Bayern Munich before moving to Stamford Bridge on a free transfer in 2006. The legendary midfielder won two FA Cups and a single Premier League title with Chelsea.