Q. What is the difference between a neurofibroma and a neuroma?
A. A neuroma is a general term that applies to any of a number of different things (neoplastic or non-neoplastic) that make a nerve or nerve bundle swell. Usually, another word is attached to give more specific meaning.
Neoplastic neuromas are tumors of any part of a nerve (including the surrounding myelin); sometimes the term is used more broadly to refer to any tumor of neural tissue. An example of a neoplastic neuroma is acoustic neuroma, a benign tumor surrounding the 8th cranial nerve (you can also call this tumor a schwannoma, since it is a neoplasm derived from the Schwann cells surrounding the nerve, not the nerve itself).
The main non-neoplastic neuromas are traumatic neuroma (a non-neoplastic reaction of a nerve to some sort of damage) and Morton’s neuroma (which is not even a neuroma, but just an accumulation of fibrous tissue around a nerve, usually in the foot).
Neurofibromas are benign neoplasms derived from the myelin sheath of peripheral nerves (just as a reminder: the myelin surrounding peripheral nerves is supplied by Schwann cells; the myelin surrounding central nerves is supplied by oligodendrocytes). They often occur in the context of neurofibromatosis, a hereditary condition characterized by multiple cutaneous neurofibromas, pigmented skin lesions, skeletal abnormalities, macrocephaly, epilepsy, and a bunch of other findings. In the photo above, the patient has multiple neurofibromas scattered over his entire body.
Neurofibromas are like schwannomas, in that they are derived from schwann cells. However, a schwannoma has mostly just schwann cells in it, whereas a neurofibroma has a bunch of other cell types, like fibroblasts, endothelial cells, and mast cells.
My book (Oxford Handbook of Clinical Medicine, 10th edition, page 462), says that a Schwannoma is not a neuroma. Here is the full quote, “Acoustic neuroma: Doubly misnamed: it is a Schwannoma (not neuroma) arising from the vestibular (not auditory) nerve.” But judging by your explanation, would you say that the book is wrong?
Hi Qasid –
I agree with the definition in your book. “Acoustic neuroma” is a commonly used term that refers to a schwannoma of the vestibular branch of the 8th cranial nerve. In that sense, it is a double misnomer! However, the term “neuroma” can be used to refer to any tumor (or swelling) of a nerve or its surrounding structures. So I think that a mention of “acoustic neuroma” (or, more accurately, “schwannoma of the vestibular branch of the 8th cranial nerve”) is warranted in any discussion of neuromas.
Robbins 9e doesn’t actually define neuroma outside of the context of specific neuromas such as Morton’s neuroma. In addition, although Robbins notes that “acoustic neuroma” is a double misnomer, it refers to the tumor variously as “acoustic schwannoma” and even “acoustic neuroma” throughout the book!
So to sum up: it’s important to understand that the tumor usually referred to as “acoustic neuroma” is actually a schwannoma that arises from the vestibular (not the acoustic) branch of the 8th cranial nerve. As such, the histologic findings are those of a schwannoma (with Antoni A and B areas and Verocay bodies). That being said, I think the double misnomer “acoustic neuroma” will probably persist, as it rolls off the tongue more easily than “schwannoma of the vestibular branch of the 8th cranial nerve.”