My sister has a 9mm pars intermedia cyst in her
Surgery is unlikely if asymptomatic.
Thanks for the query.
9mm tumor is comparatively small and generally surgery is not required for such tumors. Generally close monitoring with six monthly or yearly MRI follow up only required.
However if she develop symptoms like headache and visual disturbances or hormonal changes( unlikely in this case) surgical removal might be required.
You can consult a neurosurgeon for expert opinion.
Wishing all the best.