The Raikage and his team (Karai and Nigai) had stolen a secret scroll from Sugi Village but were infected by a parasitic, explosive insect .
Tsunade, unable to perform surgery herself due to her hemophobia (fear of blood) at the time, oversees Shizune as she performs the delicate procedure to extract the insect . Stai guardando NarutoShippuden Ep 287 SUB ITA
We learn more about her background, including the fact that her uncle was Dan Katō . The Raikage and his team (Karai and Nigai)
It falls within the Seven Shinobi Swordsmen arc of the anime's war saga . explosive insect . Tsunade