What term describes a cluster of pigmented cells that can be raised or flat on the skin?

The term that describes a cluster of pigmented cells that can be either raised or flat on the skin is "lentigines." Lentigines are also commonly referred to as age spots or liver spots and are typically characterized by their increased concentration of melanin, leading to darker patches on the skin. They can vary in size and may appear due to sun exposure or other forms of ultraviolet light over time.

While melanoma is a type of skin cancer that arises from melanocytes, it does not specifically refer to a benign cluster of pigmented cells. Freckles are small, flat, and often numerous but typically involve a more dispersed pattern of pigmentation rather than a cluster. Hyperpigmentation is a broader term that describes any area of skin that becomes darker than its surrounding skin, but it does not specifically refer to the defined clusters associated with lentigines. Therefore, lentigines accurately captures the description of clusters of pigmented cells on the skin.