A Spitz nevus is a benign

Benign

A benign tumor is a tumor that lacks the ability to metastasize. Common examples of benign tumors include moles and uterine fibroids.The term "benign" implies a mild and nonprogressive disease. Indeed, many kinds of benign tumors are harmless to human health...

 melanocytic nevus

Melanocytic nevus

A melanocytic nevus is a type of lesion that contains nevus cells .Some sources equate the term mole with "melanocytic nevus". Other sources reserve the term "mole" for other purposes....

, a type of skin

Skin

-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

 lesion, affecting the epidermis and dermis

Dermis

The dermis is a layer of skin between the epidermis and subcutaneous tissues, and is composed of two layers, the papillary and reticular dermis...

.

Spitz nevus is also known as spindle and epithelioid cell nevus and juvenile melanoma. The latter term is generally no longer used as it is misleading: it is not a melanoma, it is a benign lesion; it can also occur in adults, not only in children.

Epidemiology

Spitz nevi are uncommon. Their annual incidence

Incidence (epidemiology)

Incidence is a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate with a denominator.Incidence proportion is the...

 was estimated in a coastal population of sub-tropical Queensland

Queensland

Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...

 to be 1.4 cases per 100,000 people. For comparison, the annual incidence of melanoma

Melanoma

Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye...

 in the same population, which is high by world standards is 25.4 cases per 100,000 people.

Whilst they are most commonly found on people in their first two decades of life, the age range for people with Spitz nevi is from six months to 71 years, with a mean

Arithmetic mean

In mathematics and statistics, the arithmetic mean, often referred to as simply the mean or average when the context is clear, is a method to derive the central tendency of a sample space...

 age of twenty-two years and a median

Median

In probability theory and statistics, a median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to...

 age of nineteen years.

Pathology

The cause of Spitz nevi is not yet known. There is an association with sunburn

Sunburn

A sunburn is a burn to living tissue, such as skin, which is produced by overexposure to ultraviolet radiation, commonly from the sun's rays. Usual mild symptoms in humans and other animals include red or reddish skin that is hot to the touch, general fatigue, and mild dizziness. An excess of UV...

, but causation is not established. Genetic studies of Spitz nevi have shown that most cells have the normal number of chromosome

Chromosome

A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

s, however a minority (25%) of cells have been shown to contain extra copies of parts of some chromosomes, such as the short arm of chromosome 11

Chromosome 11 (human)

thumb|right|Chromosome 11 ChartChromosome 11 is one of the 23 pairs of chromosomes in humans. Humans normally have two copies of this chromosome. Chromosome 11 spans about 134.5 million base pairs and represents between 4 and 4.5 percent of the total DNA in cells...

 (11p).

Spitz nevi characteristically have vertically arranged nests of nevus cells that have both a spindled and an epithelioid

Epithelioid

An epithelioid cell is a cell that resembles epithelial cells in that it directly contacts its neighboring cells via cell surface molecules or junctions. Unlike epithelial cells, however, epithelioid cells make contacts over their entire surface, rather than at restricted portions. The term...

 morphology. Apoptotic

Apoptosis

Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...

 cells may be seen at the dermal-epidermal junction. The main histologic differential diagnoses are pigmented spindle cell nevus

Pigmented spindle cell nevus

A pigmented spindle cell nevus is a cutaneous condition characterized by a dark brown to black macule or papule, usually less than 6 mm....

 and malignant melanoma.

Eponym

The lesion is named after Dr.Sophie Spitz

Sophie Spitz

Sophie Spitz, M.D. was an American pathologist who published the first case series of "juvenile melanoma," , skin lesions that have come to be known as Spitz nevi....

, the pathologist who originally described it in 1948.