Giant congenital melanocytic nevus is a skin condition characterized by an abnormally dark, noncancerous skin patch nevus that is composed of pigment-producing cells called melanocytes. It is present from birth congenital or is noticeable soon after birth. The nevus may be small in infants, but it will usually grow at the same rate the body grows and will eventually be at least 40 cm The nevus can appear anywhere on the body, but it is more often found on the trunk or limbs. The color ranges from tan to black and can become darker or lighter over time.
Becker's nevus - Wikipedia
Shriner's Hospital for Children
Hairy cell leukemia cells, which appear as the darker cells in this photo, are surrounded by a halo of fine projections villi. To diagnose hairy cell leukemia, your doctor may take a sample of bone marrow from your body and examine it under a microscope to look for hairy cells. Hairy cell leukemia is a rare, slow-growing cancer of the blood in which your bone marrow makes too many B cells lymphocytes , a type of white blood cell that fights infection. These excess B cells are abnormal and look "hairy" under a microscope. As the number of leukemia cells increases, fewer healthy white blood cells, red blood cells and platelets are produced. Hairy cell leukemia affects more men than women, and it occurs most commonly in middle-aged or older adults. Hairy cell leukemia is considered a chronic disease because it may never completely disappear, although treatment can lead to a remission for years.
Almost every adult has a few of them. Clinically, dysplastic nevi may be asymmetric, have irregular borders, or have irregular color. Over time, they usually enlarge and some develop hairs. Atypical moles were first described in as distinctive pigmented skin lesions present in 37 of 58 members of six families with melanoma.
A congenital pigmented or melanocytic nevus is a dark-colored, often hairy, patch of skin. It is present at birth or appears in the first year of life. A giant congenital nevus is smaller in infants and children, but it usually continues to grow as the child grows. A giant pigmented nevus is larger than 15 inches 40 centimeters once it stops growing. These marks are thought to be caused by problems with melanocytes that don't spread evenly as a baby grows in the womb.