Dermatology Library

M

Macule:

A flat spot or patch of skin that is not the same color as the surrounding skin.

Malignant:

When referring to cancer, malignant means the ability to grow and spread in an uncontrolled manner beyond the local confines of the tumor. Its opposite, "benign," refers to a growth that is non-cancerous.

*Malignant Melanoma: See: Melanoma

Margin:

In skin cancer surgery, the amount of normal-appearing tissue removed around the tumor. Margin is usually measured in centimeters.

Tumor Thickness (millimeters) Excisional Margin (centimeters)
In situ melanoma 0.5
less than 1.0 1.0
1.0-4.0 2.0
more than 4.0 at least 2.0

Surgical margin may be modified in individual patients for medical or esthetic reasons. The main goal is complete removal of the melanoma.

See Thickness for a discussion of the relationship between tumor thickness and 5-year survival after treatment.

Also see: Skin Cancer, Melanoma

Melanin:

Skin pigment (substance that gives the skin its color). Dark-skinned people have more melanin than light-skinned people.

Melanocytes:

Cells that make the skin pigment melanin. Melanin is made in small granules, called melanosomes, within the melanocyte. Melanin is then transported to cells of the outer skin (keratinocytes), where the melanin is seen as "color" of the skin.

Melanoma:

Melanoma is a type of cancer that begins in the skin. It is completely curable when detected early, but can be fatal if allowed to progress and spread. Cancer is a condition where one type of cell grows without limit in a disorganized fashion, disrupting and replacing normal tissues and their functions, much like weeds overgrowing a garden. Melanoma is a cancer of the pigment producing cells in the skin, known as melanocytes. Normal melanocytes reside in the outer layer of the skin and produce the brown pigment melanin, which is responsible for the color of our skin. Melanoma is when melanocytes become cancerous, grow, and invade other tissues.

Also see topics in: Skin Cancer

Melasma:

A skin condition presenting as brown patches on the face of adults. The most common sites of involvement are the cheeks, bridge of nose, forehead, and upper lip. Melasma occurs mostly in women. Only 10% of those affected are men. Dark-skinned races, particularly Hispanics, Asians, Indians, people from the Middle East, and Northern Africa, tend to have melasma more than others.

Metastasis:

The spreading of disease from one part of the body to another part. Melanoma metastasizes most often to lymph nodes, liver, abdomen, lungs, bone, skin, heart, and brain.

Microdermabrasion:

See: Dermabrasion

Minoxidil:

See: Hair Loss

Mohs surgery:

In certain situations, your dermatologist may refer you for a specialized technique called Mohs micrographically controlled surgery. In this method, performed by specially trained dermatologic surgeons, the skin cancer is removed under local anesthesia in an office setting and microscopic sections are prepared on slides while you wait. Your Mohs surgeon examines the slides to determine if all the cancer cells have been removed. If not additional layers are taken until the cancer is completely excised. The advantage of this technique is that a minimum amount of tissue is removed and all the edges of the specimen are carefully studied. This method has a high cure rate, but is not required for all skin cancers. In general, most dermatologists agree that recurrent skin cancers (skin cancers that were previously treated and have come back, incompletely removed skin cancers, large skin cancers, and skin cancers in cosmetically important areas), may benefit from the Mohs technique. After the skin cancer has been removed using this method, it maybe allowed to heal naturally or reconstructive surgery using a skin flap or skin graft may be performed.

Also see: Skin Cancer, Dermatologic Surgery

Moles:

Everyone has moles (also known as "nevi"), sometimes 40 or more. Most people think of a mole as a dark brown spot, but moles have a wide range of appearance. They can be raised from the skin and very noticeable, they may contain dark hairs, or they may be dangerous. Moles can appear anywhere on the skin, alone or in groups. They are usually brown in color and can be various sizes and shapes. The brown color is caused by melanocytes, special cells that produce the pigment melanin. Moles probably are determined before a person is born. Most appear during the first 20 years of a person's life, although some may not appear until later in life. Sun exposure increases the number of moles. Each mole has its own growth pattern. At first, moles are flat and tan, pink, brown or black in color, like a freckle. Over time, they usually enlarge and some develop hairs. As the years pass, moles usually change slowly, becoming more raised and lighter in color. Some will not change at all. Most moles will slowly disappear, seeming to fade away. Others will become raised so far from the skin that they may develop a small "stalk" and eventually fall off or are rubbed off. This is the typical life cycle of the common mole. These changes occur slowly since the life cycle of the average mole is about 50 years. Moles may darken, with exposure to the sun. During the teen years, with birth control pills and pregnancy, moles often get darker and larger and new ones may appear.

Molluscum contagiosum:

Molluscum contagiosum is a common skin disease caused by a virus which affects the top layers of the skin. The name molluscum contagiosum implies that the virus develops growths that are easily spread by skin contact. Similar to warts, this virus belongs to the poxvirus family and enters the skin through small breaks of hair follicles. It does not affect any internal organs. Molluscums are usually small flesh-colored or pink dome-shaped growths that often become red or inflamed. They may appear shiny and have a small indentation in the center. Because they can spread by skin-to-skin contact, molluscums are usually found in areas of skin that touch each other such as the folds in the arm or the groin. They are also found in clusters on the chest, abdomen, and buttocks and can involve the face and eyelids.

Monkey Pox:

Monkeypox is a rare viral disease that is found mostly in the rainforest countries of central and west Africa. The virus can spread to humans from an infected animal through an animal bite or direct contact with the animal's lesions or body fluids. Although it is much less infectious than smallpox, the disease also can be spread from person to person through large respiratory droplets during long periods of face-to-face contact or by touching body fluids of a sick person or objects such as bedding or clothing contaminated with the virus.

Mouth Care:

Gum disease, halitosis, mouth ulcers and sensitive teeth are all problems which fall under oral health and which do not necessarily require a trip to the dentist. Each one is discussed in detail below.

GUM DISEASE (PERIODONTAL PROBLEMS)

Periodontal problems affect the supporting tissues of the teeth and are related to poor gum management. They constitute the major dental risk to the adult population. The most important cause is accumulation of plaque which leads to bacterial growth and subsequent inflammation. There are two major conditions, gingivitis and the more severe periodontitis.

GINGIVITIS

Plaque which accumulates at the tooth gum junction harbours various bacteria which produce metabolites. These metabolites, which include inflammatory agents, are secreted into the local gum. This results in capillary dilatation and oedema, the redness and swelling which are symptoms of the condition.

If the plaque and its associated bacterial colony are not removed, the degradatory process continues leading to decreased venous return and a bluish tinge of deoxygenated blood being observed.

PERIODONTITIS

Gingival epithelial cells are attached to tooth enamel at the gum tooth junction. As a consequence of bacterial action, there may be loss of this epithelial attachment causing the development of 'pockets'. These may be 3-4mm deep and they harbour food particles and bacteria. This also leads to gum recession.

If this is not resolved the condition worsens. The marginal gingivae is normally attached to the teeth by a network of collagen fibres which is called the periodontal ligament. This ligament may become weakened and alveolar bone is irreversibly lost.

The tooth becomes loose and there is a danger of further bacterial attack with the development of abscesses, and eventual tooth loss.

HALITOSIS

Some degree of bad breath is normal first thing in the morning. This is the result of reduced tongue activity and salivary flow during the night. There is a build up of a high concentration of malodorous sulphur compounds produced by bacteria overnight which results in halitosis. Mouth breathers also suffer more from morning halitosis.

Bad breath at other times may indicate a problem. As many as 85 per cent of halitosis cases are caused by problems in the oral cavity. Gingivitis, periodontitis and caries are common causes, while oral cancer may be implicated in extreme cases.

However, non-oral causes are well known. These include sinusitis, tonsillitis and rhinitis. Gastric problems as well as diet may be the cause. Highly odorous foods and drinks give off smells which may 'leak' from the stomach. These include onions, garlic, spicy foods and alcohol. These are also excreted from the lungs giving rise to halitosis many hours after ingestion.

Halitosis of short duration may be due to the stomach being empty. Other rarer causes include tuberculosis and acute serious illness such as typhoid fever.

APHTHOUS ULCER

About a fifth of the population suffer from mouth ulcers in any one year. US surveys indicate they are most common in patients who are stressed and that a slightly increased proportion of females are affected.

Single isolated traumatic ulcers are often due to catching the gum with the toothbrush or hard food.

The cause of recurrent aphthous stomatitis is largely unknown. Many factors appear to be involved, including genetic predisposition, hypersensitivity to normal mouth bacteria, food allergies, hormonal changes, systemic disease and nutritional deficiency. Recent research has implicated the immune system and a specific trigger event (stress, trauma, female cycle).

Aphthous ulcers range from 0.3-3cms in diameter and occur on the non-keratinised mucosal surfaces of the mouth such as the cheeks, tongue and gums. They have depressed round grey area and a red erythomatous edge. They may be extremely painful, inhibiting eating.

HYPERSENSITIVE TEETH

Many patients develop teeth sensitivity and it may be related to gum recession, exposing the cementum/enamel junction. Other cases include excessive brushing with a hard toothbrush and use of abrasive toothpastes or powders. Gum recession is common in old age.

Reversal of gum recession should be the major aim of treatment. Sensitivity caused by the nerves being more accessible may be treated by specific toothpastes designed to 'block the pores' in the enamel. The strontium ion is believed to block nerve access and is thus useful.

A second mechanism is to reduce nerve transmission using the potassium ion. Fluoride is also incorporated in some toothpastes designed for sensitive teeth.

Applying these toothpastes directly to teeth with a finger is more effective than traditional brushing.

Mucocutaneous candidiasis:

A mycotic infection of the skin and mucous membranes usually caused by the yeast, Candida albicans. However, other Candida species are occasionally responsible. It is a common disorder that affects all age groups, with no sex, race, or ethnic predilection. Mucocutaneous candidiasis is more common in persons who wear dentures, have diabetes mellitus, and in those immunocompromised by disease or by therapy. Most patients have disease limited to the cutaneous surfaces, especially areas of skin folds. However, immunocompromised persons may develop extensive cutaneous involvement. In some patients a serious, even life-threatening, systemic infection may develop. Systemic candidiasis is not addressed here.

Mucous membrane involvement may be a marker for an immunocompromised state. The presence of oral candidiasis, especially in adults, may be an initial manifestation of diabetes mellitus, leukemia, lymphoma, malignancy, neutropenia, and HIV infection. Genital candidiasis may affect the vulva and vaginal area, as well as the perineal and groins, causing candidal intertrigo. Candidiasis may also affect the nail unit, particularly the nail plate and paronychial area.

Mycotic Infection:

Fungal infection