Webster's New World Medical Dictionary

melanocyte
A cell in the skin that produces and
contains the pigment melanin.
melanoma
The most dangerous form of skin
cancer, a malignancy of melanocytes, the cells that
produce pigment in the skin. Melanoma is most
common in people with fair skin, but it can occur in
people with all skin colors. Most melanomas pres-
ent as dark, mole-like spots that spread and, unlike
moles, have irregular borders. The tendency toward
melanoma may be inherited, and the risk increases
with overexposure to the sun and sunburn. The use
of sunscreens can decrease the risk of developing
melanoma and other skin cancers. Malignant
melanoma is classified into four clinical types: acral
lentiginous melanoma, superficial spreading
melanoma, nodular melanoma, and lentigo maligna
melanoma. Anyone who has concern about an
unusual mole-like spot should see a physician.
Melanoma is highly curable when detected early. 
melanoma, acral-lentiginous
A type of malig-
nant melanoma that is uncommon in white people
but the most common type in nonwhite people.
Acral-lentiginous melanoma starts as an irregular
enlarging black flat spot (macule), most often on
the palm of the hand and the sole of the foot, less
often on a mucosal surface, such as the vulva or
vagina.
melanoma, amelanotic
A colorless melanoma
that is detectable only on close examination of the
skin.
melanoma, choroidal
See 
melanoma, ocular.
melanoma, lentigo maligna
One of the four
clinical types of malignant melanoma and the slow-
est growing type. Lentigo maligna melanoma typi-
cally begins as a patch of mottled pigmentation that
is dark brown, tan, or black on sun-exposed skin,
such as on the face.
melanoma, nodular
One of the four clinical
types of malignant melanoma, which typically pres-
ents as a raised, distinct, bluish-black tumor that
may be encircled by particularly pale skin, most
often in middle-aged or older adults.