My father his age is 57 years old and he is having
diabetes since 8 years and he is also having a problem of diabetic eye retinopathy since 3 years and he is taking injection for eye and he was having a cyst in behind head and it was small in size and it is getting big and sometimes sizes r fluctuating big and small and I hav attached a photo of it and kindly suggest wt to be done and is it dangerous?