Final answer:
Pigmented lesions can be benign or indicative of serious conditions like melanoma, which presents as large brown or black patches with uneven borders. Lesions on typically unexposed areas like palms and mucous membranes are particularly concerning. Other pigmentation disorders such as vitiligo and Addison's disease, while not being directly life-threatening, significantly impact quality of life.
Step-by-step explanation:
Pigmented lesions are a common dermatological concern, and some special cases require careful attention due to their potential for malignancy. One such case involves melanomas, which often present as large brown or black patches with uneven borders and a raised surface (Figure 5.20). These lesions may also be sprinkled with darker specks, adding to the irregularity of their appearance. Another worrying feature is a small lesion with an irregular border and parts that appear red, white, blue, or blue-black, which may suggest a high risk of cancer.
Additionally, dark lesions found on the palms, soles, fingertips, toes, or mucous membranes can be of particular concern because these areas are not typically exposed to the sun, and lesions there can indicate acral lentiginous melanoma, a rare form of melanoma.
While pigmented lesions like these can be signs of serious conditions, there are nonmalignant disorders of pigmentation such as vitiligo, which results in the depigmentation and the appearance of lighter colored patches of skin. This condition is more noticeable on darker skin but is not often directly life-threatening (Figure 5.10). Similarly, hyperpigmentation, such as seen in Addison's disease, also affects the skin's appearance, characterized by darkened skin that may return to a more normal pigment with treatment (Figure 12.6.5). Although both albinism and vitiligo affect the skin's pigmentation, neither is typically life-threatening, though they may have significant impacts on quality of life.