If acoustic neuroma not treated, will it grow bigger and bigger and shows itself on the skin/upper skin?

No: Untreated acoustic neuromas will not likely show themselves on the skin because they are intracranial masses, i.e. Your skull is in the way, and it is not likely to bulge. That being said, acoustic neuromas can grow bigger and compress nearby structures including the vestibulocochlear and facial nerves, resulting in hearing loss and facial paralysis.

No: An acoustic neuroma occurs deep within the skull in the internal auditory canal allong the course of the 8th cranial nerve. It grows inward, not toward the skin. Symptoms are decreased hearing, ringing of the ears, and balance troubles. They are usually slow-growing but can cause major trouble if untreated for a long time. There are other types of neuromas that cause lumps in the skin.

Can expand: The neuroma should be followed by serial mri's, and is likely to slowly grow, but will not leave the cranial cavity and appear on the skin. However, expansion will cause loss of hearing, dizziness, decreased facial and eye sensation, and perhaps double vision, other facial nerve problems, with loss of balance. Have a good neurosurgeon follow this closely.

No: Acoustic neuromas are tumors located in the posterior fossa, specifically the cerebello-pontine angle. Therefore as it grows larger it puts more and more pressure on the cerebellum and brainstem, and into the acoustic canal where it puts more pressure on the 7th and 8th cranial nerve. It shouldn't ever come outside of the skull.