When to Consult a Dermatologist
If you have noticed changes in the texture or appearance of your skin—particularly, new moles or patches of discoloration—it is best to consult a dermatologist for further examination.
What is Acral Nevus?
Acral nevus is a type of benign tumor that develops from melanocytes, a type of cell in the skin that produces the pigment melanin [1, 2]. As the name suggests, acral nevus impacts the acral skin, which is the topmost layer of the epidermis that covers the palms of the hands, soles of the feet, fingers, toes, and fingernails [3].
Acral nevus is characterized by clusters of melanocytic nevi—non-cancerous growths [4]—on the acral skin. These nevi are usually localized to a particular area of the body, such as the palms, soles of the feet, or nail matrix. Lesions are often flat, asymmetrical, and have irregular borders [5].
What is Melanoma?
Melanoma is a type of skin cancer originating from cells that produce the pigment melanin, known as melanocytes. It is considered the most aggressive form of skin cancer and has high invasive and metastatic potential [6]. When melanoma predominantly impacts the acral skin, it is referred to as acral lentiginous melanoma (ALM) or, more simply, acral melanoma [3].
Melanoma typically starts as a dark mole on the skin. These moles display a characteristic “parallel ridge pattern,” in which darker pigmentation is seen along the raised ridges of the surface skin [1].
Differences Between Acral Nevus and Melanoma
Acral nevus and acral melanoma can be difficult to distinguish between, since they are both abnormal growths that impact the acral skin. However, acral nevus and melanoma are distinct conditions and can be differentiated in several ways.
Appearance of Acral Nevus vs Melanoma
As mentioned earlier, a key feature of melanoma is the parallel ridge pattern. This feature is absent in cases of acral nevus; instead, pigmentation tends to be concentrated along the indented furrows of the skin markings (parallel furrow pattern) [1]. While this difference in visual appearance is not a definitive way to distinguish acral nevus from melanoma, it can help dermatologists assess the likelihood of whether a melanocytic nevus is benign or malignant.
Genetics of Acral Nevus vs Melanoma
Genetic analysis of tissue samples from acral nevus versus acral melanoma have suggested that the two conditions have different mutational underpinnings. Duplications of the genes CCND1 and MYC have been associated with acral melanoma, as have losses of the gene CDKN2A [3]. In contrast, benign acral nevi have been linked to mutations in genes involved in the MAP kinase pathway, such as BRAF, NRAS, and MAP2K1 [7]. While BRAF can also be mutated in cases of melanoma, the nature of the mutation differs. In acral nevus, the mutated BRAF protein typically results from a valine to glutamate amino acid substitution at residue 600 (V600E). By contrast, BRAF mutations in melanoma are typically non-V600E [7]. Moreover, KIT, NF1, and TERT promoter mutations, which are often present in acral melanoma, have not been consistently observed in acral nevus [7].
Prognosis of Acral Nevus vs Melanoma
The prognosis for acral nevus also differs from that of acral melanoma. Acral melanoma has a poorer prognosis than acral nevus due to the aggressive nature of the tumors and potential for metastasis. By contrast, acral nevus is a benign condition and therefore is unlikely to cause serious issues.
Conclusion
Acral nevus and melanoma are two conditions which result from abnormal growth of melanocytes. However, acral nevus is a benign condition, whereas melanoma is a form of cancer. The two conditions may appear visually similar because they both result in skin discoloration and impact similar areas of the body. Acral nevus can be distinguished from acral melanoma because it lacks the parallel ridge pattern characteristic of melanomas and exhibits a different mutational profile. Occasionally, acral nevus can progress to melanoma, but evidence suggests that this occurs infrequently. Changes in skin coloration, along with the occurrence of new moles or lesions, should be discussed with your dermatologist, and any benign lesions should be monitored over time to ensure that they do not become cancerous. Most of the time, skin spots are nothing to worry about; however, it is better to err on the side of safety.