I would think that in three years, you deserve some follow up. I would go and get to the doctor and get a scan and get an exam.
Numbness and tingling can be so many things - even a mineral deficiency as well as nerve issues. Depending on the severity, it should be checked.
Neurologists may be very quick to tell you that you are fine with a pineal cyst and that it is not causing your symptoms. But beware: 1) Doctors in general don't really understand what the pineal gland does; and 2) Some don't seem to understand the difference between symptomatic and asymptomatic pineal glands and tell their patients not to worry about pineal cysts.
Some things to keep in mind, according to the medical literature:
1) The most common symptom is headaches, followed by vision problems and dizziness, and in some cases insomnia, nausea and cognitive deficits, particularly if cognitive deficits are involved. More rare is numbness and tingling. In extreme cases, pineal cysts can result in loss of consciousness and seizure disorder. So please take this seriously, particularly if the cyst is causing intracranial pressure such as hydrocephalus.
2) Pineal cysts can be symptomatic if they are larger than 0.5 cm. Problems occur when the cysts cause compression in the brain, or when they are associated with apoplexy or hydrocephalus.
3) Radiologists cannot easily distinguish between cysts and benign tumors, often leading to misdiagnosis. NOTE: A benign tumor is not metastatic, not malignant. It is extremely, extremely rare to get a malignant, metastatic tumor in the pineal gland, so please do not worry about this unless your radiologist/doctor has told you otherwise.
4) It is common that patients are told that the pineal cyst cannot be affecting them after a neurological test. But note that some patients present no neurological symptoms in these tests, while still having the symptoms in 1) above.
5) If you are in the 18-34 age group, your cyst can grow, so you should get MRIs every 3-6 months. If your doctor does not want to, get a new doctor.
5) If you have to get surgery, get the following one but only if you have compression or hydrocephalus and your symptoms are incapacitating: Suboccipital craniotomt with infratentorial-supracerebellar approach and microsurgical resection of pineal cyst. Contrary to what is stated above, this is NOT brain surgery. They access your pineal region from beneath the brain, so they do not affect your brain at all. It sounds like a scary procedure but is actually straightforward for a good brain neurosurgeon. The surgeon essentially inserts a microscopic endoscope that magnifies the area by 50x and uses a navigation system to get him there. It is minimally invasive. The medical literature says that most patients whose pineal cysts are not too large (e.g., < 4.5 cm) become completely asymptomatic after surgery. The surgery entails a 6-8 week recovery, and a small incision in the head and removal of skull bone, which grows back after surgery. The biggest risk associated with surgery is infection, as with any other surgery.
The most important thing is to get a doctor who takes your pineal cyst seriously. It is a rare disorder, and few doctors understand it well. So you will need to be persistent.