Stereotactic surgery or stereotaxy is a minimally-invasive form of surgical intervention which makes use of a three-dimensional coordinates system to locate small targets inside the body and to perform on them some action such as ablation (removal), biopsy, lesion, injection, stimulation, implantation, radiosurgery (SRS) etc.
In theory, any organ system inside the body can be subjected to stereotactic surgery. Difficulties in setting up a reliable frame of reference (such as bone landmarks which bear a constant spatial relation to soft tissues), however, mean that its applications have been limited to brain surgery. Besides the brain, biopsy and surgery of the breast are done routinely to locate, sample (biopsy) and remove tissue. Plain X-ray images (radiographic mammography) and computed tomography can be used to guide the procedure.
Stereotactic radiosurgery can successfully treat many different types of tumors, both benign and malignant. The malignant brain tumors treated most often are the “brain metastases” or tumors that have spread to the brain.
Learn more at Stereotactic surgery on Wikipedia