CMN and Nevus Terms Glossary


This guide was designed to help you understand the terminology you may encounter with regard to large/giant congenital melanocytic nevi (CMN) and neurocutaneous melanocytosis (NCM). It briefly defines, in layman’s terms, the technical terminology used by doctors and medical professionals. If you have further questions after reviewing this glossary, please contact your doctor or Nevus Outreach.


Removal of a small piece of tissue for microscopic examination for diagnostic purposes.

Brain Regions

A diagram showing the regions of the brain


Uncontrolled growth of cells.


Present at birth or within the first year of life.


A substance, or dye, given in the vein, to enhance the MRI or CT films.

CT Scan (Computed Tomography)

Also called CAT (Computed Axial Tomography) A diagnostic tool for the examination of the body, such as the brain. CT is generally less expensive but less sensitive than MRI in detecting abnormalities.

Cultured Epithelial Autografts

See cultured skin.

Cultured Skin

One limited option of treatment for a nevus. Small sections of the superficial layer (epidermis) of the patient’s normal skin are removed and then allowed to grow in the laboratory. Once they have grown sufficiently large they can be used as thin grafts to cover an excised nevus.


A tube or wick sometimes inserted during an operation to ensure that any fluid accumulated beneath the skin is immediately removed. Typically inserted within the wound beneath undermined areas or a transposed flap.

EEG (electroencephalogram)

Amplification, recording, and analysis of the activity of the brain. An EEG is helpful in diagnosing seizures and other convulsive disorders.

EMLA™ (Eutectic Mixture of Local Anesthetics)

A cream used to numb the skin before laser treatments.


To cut away or take out surgically.


An area of skin and subcutaneous tissue that can be elevated and moved to an adjacent area.


A dye, given in the vein, that is used as a contrast during MRI to help diagnose mass lesions in patients with NCM.


There are two types of hair:


Soft, colorless hair


Thick, coarse, colored hair


A condition that may be transmitted from one generation to the next.


Enlargement of the brain ventricles because of increased fluid. Nevus cells inside the central nervous system blocking the circulation of fluid can be the cause.


A surgical cut.


The inner two layers of membranes that cover the brain and spinal cord. The two layers are the arachnoid and pia mater. 

MRI (Magnetic Resonance Imaging)

A diagnostic tool useful for examining the central nervous system including the brain and spinal cord.


An uncontrolled growth of cells that can spread throughout the body.


The pigment particles that give color to hair, skin and eyes.


A cell that produces melanin.


A tumor or mole that is malignant.


Abnormal deposits of melanocytes usually resulting in dark pigmentation.


The presence of an excessive number of melanocytes.


The three membranes that surround the brain and spinal cord, called the dura mater, arachnoid and pia mater. The inner two layers are called the leptomeninges.


A collection of pigmented cells in the skin.


See nevus.


Affecting both the skin and nerves.


Plural of nevus.


Cells composing nevi or moles.


A mole or pigmented birthmark.


Swelling of the optic disk caused by increased pressure within the brain.


Any organic coloring matter.

Posterior Axial

Along or covering the spine.


Any sudden and recurring abnormal functioning of the brain. In order of severity, seizures can be classified as:


Confined to one part of the body. These can generalize and become grand mal seizures.

Petit Mal

Brief absences of awareness, no muscle spasms

Grand Mal (also called clonic-tonic)

Unconscious muscle spasms, loss of consciousness. 

Serial Excision 

Having several surgeries done over time to remove a large congenital melanocytic nevus.


A diagram showing the parts of skin


Upper protective layer of skin


“Working” layer of skin, contains hair follicles and other skin structures

Subcutaneous Fat (adipose tissue)

Thin layer of padding, sometimes not found under “nevus skin.”

Skin Graft 

Using healthy skin from one area of the body to cover a part that has lost its skin. This may be full thickness (including all of the dermis) or split/partial thickness (including only part of the dermis).

Simple Excision 

A single surgical removal.

Tissue (Skin) Expansion 

Expandable bags are placed under the uninvolved skin and slowly inflated with saline. This causes more uninvolved skin to be created and this extra skin can be used to replace part of a nevus removed during a surgical excision, allowing more nevus to be removed.

V-P Shunt (Ventricular-Peritoneal Shunt)

Tube connecting the ventricles of the brain to the abdominal cavity. A passage connecting two anatomical channels and diverting blood or other fluid from one to the other.