DIfferential Diagnosis for Melanoma

Seborrheic keratosis
- benign wart-like growths on the surface of the skin.
- cause is unknown. The condition commonly appears after age 40.
Symptoms:
1) located on the face, chest, shoulders, back, or other areas
2) usually painless, but may become irritated and itch
3) yellow, brown, black, or other colors
4) slightly elevated, flat surface
5) May have a rough or wart-like texture
6) Often have a waxy surface
7) Have a round-to-oval shape
8) May have a "pasted-on" appearance
9) May be single, but are usually multiple growths
Diagnosis is based primarily on the appearance of the growths. A skin lesion biopsy may be used to confirm the diagnosis.

Traumatized or irritated nevus
- may be partially avulsed and/or have hemorrhagic crusting suggesting ulceration.
- Melanocyte hyperplasia develops superficial to the scar resulting in uneven pigmentation and irregular outlines as pigment extends into the surrounding skin (quite suggestive of melanoma)
- recurrent nevus phenomenon can resemble melanoma histologically, as well.
- The history of trauma or biopsy along with review of the original biopsy helps exclude a diagnosis of melanoma.

Basal cell carcinoma
- grows by direct extension and appears to rely on the surrounding supportive tissue to grow – thus does not metastasize through blood vessels or lymphatics.
- starts in the top layer of the skin called the epidermis.
- grows slowly and is painless.
- A new skin growth that bleeds easily or does not heal well may suggest basal cell carcinoma.
- The majority of these cancers occur on areas of skin that are regularly exposed to sunlight or other ultraviolet radiation, may also appear on the scalp.
Features:
Pearly or waxy
White or light pink
Flesh-colored or brown
In some cases the skin may be just slightly raised or even flat.
May have:
A skin sore that bleeds easily
A sore that does not heal
Oozing or crusting spots in a sore
Appearance of a scar-like sore without having injured the area
Irregular blood vessels in or around the spot
A sore with a depressed (sunken) area in the middle

Lentigo
- a spot on the skin that is darker (usually brown) than the surrounding skin. Lentigines are more common among whites, especially those with fair skin.
- sometimes called an age spot or freckle
Types:
Lentigo simplex (eg, simple lentigo, juvenile lentigo) is the most common form of lentigo
Solar lentigo (eg, actinic lentigo, senile lentigo, sun spot, liver spot) is the most common benign sun-induced lesion that occurs in sun-exposed areas.
Ink-spot lentigo (ie, reticulated black solar lentigo) can be distinguished by a wiry or beaded, markedly irregular outline; these lesions occur in patients of Celtic ancestry.
PUVA lentigo is a persistent, pale brown macule appearing 6 months or longer after the start of PUVA therapy for psoriasis.
Radiation lentigo resembles UV-induced lentigo, but it often includes other histopathologic signs of long-term cutaneous radiation damage such as epidermal atrophy, subcutaneous fibrosis, keratosis, and telangiectasias.
Tanning-bed lentigines usually occur in women with a history of tanning-bed use.
Vulvar and penile lentigo are benign lesions similar to labial melanotic macules.
Lentigines profusa (ie, generalized lentigines) is characterized by numerous lentigines without signs of associated abnormalities or triggering factors.

Angiokeratoma
- A harmless, discolored, raised skin lesion involving damaged blood capillaries.
- The lesion ranges in color from red to blue and the skin involved is usually thickened.
- Red to blue skin lump
- Localized thickening of skin
Causes of Angiokeratoma
Fucosidosis
GM1 gangliosidosis, type 2
Fabry's disease
Angiokeratoma circumscriptum
Angiokeratoma of Fordyce

Venous lake
- manifest as dark blue-to-violaceous compressible papules caused by dilation of venules.
- exacerbated by solar exposure and damage
- Vascular thrombosis play a role in development

Hemangioma
- an abnormal buildup of blood vessels in the skin or internal organs.
- About 30% of hemangiomas are present at birth. The rest appear in the first several months of life.

May be:
In the top skin layers (capillary hemangioma)
Deeper in the skin (cavernous hemangioma)
A mixture of both

- A red to reddish-purple, raised sore (lesion) on the skin
- A massive, raised tumor with blood vessels
- Most hemangiomas are on the face and neck.
Hemangiomas are diagnosed by a physical examination. In the case of deep or mixed lesions, a CT or MRI scan may be performed.

Dermatofibromas
- a firm, red-to-brown, small papule or nodule composed of fibroblastic tissue. It usually occurs on the thighs or legs.
- Benign tumour
- Cause is unknown
- Most are asymptomatic, but some itch or ulcerate following minor trauma.
- Diagnosis is clinical; lesions typically dimple when grasped between the fingers

Pigmented actinic keratosis
- a precancerous growth on the skin.
- caused by sun exposure.
- occurs most commonly in fair skin, especially in the elderly and in young people who have light skin.
- Rough and dry skin lesion
- patch or growth on the skin
- Limited to one area (localized)
- Located on the face, scalp, back of the hands, chest, or other sun-exposed areas
- Gray, pink, red (erythematous), or the same color as the skin
- Begins as flat and scaly areas
- Later develops a hard and wart-like or gritty, rough, and "sandpapery" surface -- may develop a horn-like texture
- The skin lesion may be easier to feel than to see.
The health care provider makes the diagnosis based on the appearance of the skin growth. A skin biopsy may reveal any cancerous changes, if they occur.

Reference:
http://www.aafp.org/afp/20010401/1359.html
http://www.merriam-webster.com/medical/seborrheic%20keratosis
http://www.wrongdiagnosis.com/a/angiokeratoma/intro.htm
http://emedicine.medscape.com/article/1056397-overview
http://www.childrenshospital.org/az/Site998/mainpageS998P0.html
http://emedicine.medscape.com/article/1085199-overview
http://www.aad.org/public/publications/pamphlets/common_growths.html
http://www.merck.com/mmpe/sec10/ch127/ch127b.html