Neuroma vs. neurofibroma

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.

How do steroids inhibit the immune response?

Q. We heard in class today that steroids are used for autoimmune diseases, and I’ve heard this before but never understood why. What is it about steroids that make them effective as immunosuppressants?

A. There are lots of mechanisms by which steroids dampen the immune response. Here are a few of them:

1. Suppression of T cells. Steroids interfere with production of cytokines (like interleukins), which are critical in the proliferation and interaction of T cells.

2. Suppression of B cells. Steroids interfere with the binding of interleukins to B cells, which means that the B cells have a hard time proliferating and making antibodies.

3. Suppression of neutrophils. Steroids inhibit just about everything that neutrophils do: adhesion, chemotaxis, phagocytosis, and the release of toxic substances.

4. Suppression of macrophages. Steroids down-regulate the expression of Fc receptors on macrophages – so macrophages are less able to phagocytose opsonized things.

5. Diminished production of prostaglandins and leukotrienes. Steroids inhibit cyclooxygenase and phospholipase A2, which decreases the production of pro-inflammatory arachadonic acid metabolites.

Steroids are used in a ton of different immune and inflammatory disorders, like asthma, vasculitis, arthritis, gout, multiple sclerosis, sarcoidosis, alopecia areata…the list goes on and on.

What’s ringworm?


Ringworm is a superficial fungal infection of the skin, nails, or hair. The causative agent is not a worm, but a type of mold called a dermatophyte (“skin plant”). (more…)