Cafe au lait spot: A flat spot on the skin that is the color of coffee with milk (café au lait) in persons with light skin, or a darker appearance (café noir) than the surrounding skin in persons with dark skin. About 10% of the general population have cafe au lait spots. Café au lait spots are in themselves harmless, but in some cases they may be a sign of neurofibromatosis. The presence of 6 or more café au lait spots each of which is 1.5 centimeters or more in diameter is diagnostic of neurofibromatosis. Conversely, most people with neurofibromatosis who are at least 5 years old have 6 or more cafe au lait spots 1.5 centimeters or more in diameter.