Common Nevus Rainer Hofmann-Wellenhof and H

Chapter III.7 Common Nevus Rainer Hofmann-Wellenhof and H. Peter Soyer III.7

Contents vironmental factor for the development of common nevi. According to the current model of III.7.1 Definition ...... 102 the natural evolution of common melanocytic III.7.2 Clinical Features ...... 102 nevi, these nevi begin as simplex lentigo, and III.7.3 Dermoscopic Criteria...... 102 then develop into junctional and later com- pound and dermal nevi. Finally, they completely III.7.4 Relevant Clinical Differential vanish or end as fibrotic papule (Unna’s concept Diagnoses ...... 103 of “Abtropfung”; see Chap. III.1). III.7.5 Histopathology...... 103 Epidemiological studies have consistently shown that the total number of melanocytic III.7.6 Management...... 103 nevi is one of the strongest risk factors for the III.7.7 Case Study...... 103 development of melanoma. The relative risk cal- References...... 104 culated in a meta-analysis was 6.3 for persons with more than 100 common nevi compared with persons with less than 15 nevi. The exact role of common nevi as precursors of melanoma III.7.1 Definition is still under debate.

There is much debate regarding the term common or typical nevus. In our view of melano- III.7.2 Clinical Features cytic nevi, you can clinically and dermoscopi- III.7 cally differentiate between common/typical and The common nevus is a round or oval macule or uncommon/atypical or dysplastic nevi. The flat papule with regular border and homoge- term common nevus encompasses the flat com- neous color. The color can vary from all shades mon nevus, the dermal nevus of the face (Mie- of brown to black (Fig. III.7.1). The diameter is scher nevus), and the papillomatous dermal ne- smaller than 6 mm. Common nevi are found vus of Unna. These two types of nevi are mostly in skin that has been exposed to sun- described in Chaps. III.13 and III.19. light, but they may be seen on the entire skin. Common nevi are the most frequent melanocytic neoplasms. The number of common melanocytic nevi varies in different studies and is III.7.3 Dermoscopic Criteria age dependent. Common nevi usually develop most frequently at puberty. In Caucasians the The common nevus displays a regular overall mean number of common nevi varies between architecture. Most often the global pattern is re- 30 and 70 in the age between 30 and 40 years, ticular, but globular or homogenous patterns whereas in darker ethnic races common nevi are also common (Fig. III.7.2). No combinations are less frequent. Besides host factors, such as of these global patterns are observed. The color pigmentary traits and hereditary factors, expo- is equally distributed and uniform. The com- sure to UV radiation is the most important en- mon nevus lacks specific local criteria. Chapter III.7 Common Nevus Chapter III.7 103

Common Nevus III.7.5 Histopathology Rainer Hofmann-Wellenhof and H. Peter Soyer III.7 Flat common nevi are small, symmetric, sharply demarcated melanocytic lesions which are con- fined to the epidermis and papillary dermis. The melanocytes are arranged in a small nest of similar size and shape. The nests are situated predominantly on the tips of the rete ridges. Some equally distributed single melanocytes may be present. Cytomorphologically, the cells are uniform round or ovoid with monomor- phous nuclei. A sparse lymphocytic infiltration Fig. III.7.1. Two common nevi on the chest of a 37-year- may be found in the papillary dermis. old man. The nevi are smaller than 4 mm and are regularly shaped and pigmented III.7.6 Management Common nevi do not require special treatment or follow-up. Individuals should be advised to perform self-examination with special alertness to changes in shape or color. Individuals with more than 100 common nevi should visit a dermatologist once a year for total-body examination.

III.7.7 Case Study

Patient comment Fig. III.7.2. Dermoscopic image of two common flat nevi. The larger nevus has a diameter of 3 mm. Both nevi A 31-year-old woman visited the office of the are symmetric, uniform pigmented, and regularly bor- dermatologist because she noticed two new nevi dered. The smaller nevus displays a prominent regular after the summer vacation. pigment network, whereas in the larger nevus there is only a faint network Questions asked by the physician

III.7.4 Relevant Clinical Differential Do you still mention a growth or another change Diagnoses of the new nevi? Since in our view lentigo simplex represents a precursor of the flat common nevus, both can Clinical image including be separated only histopathologically. Solar len- detailed description tigo or actinic lentigo tend to be lighter than common nevi and are more irregularly bor- Clinical examination revealed some flat nevi, dered. all with a diameter fewer than 4 mm on the trunk and extremities. 104 R. Hofmann-Wellenhof, H.P. Soyer

Comments

The clinical diagnosis of common flat melanocytic nevus is undemanding. Dermoscopy serves more to calm concerned patients than to confirm the diagnosis. Patients should be advised to perform self-examination and apply sun protection.

Dermoscopic image including C Core Messages detailed description ■ Common flat melanocytic nevi are the most frequently melanocytic neo- Dermoscopic features of one nevus on the back plasms. revealed a uniform pigmented homogeneous ■ Common flat nevus requires no special pattern. The small depigmented area on the top treatment. III.7 of the lesion corresponded to the typical hy- ■ More than 100 common melanocytic popigmentation around a hair follicle. nevi indicate a significantly higher risk of developing melanoma.

Clinical diagnosis including relevant differential diagnosis References The diagnosis of a common flat melanocytic nevus was made without any difficulty. 1. Zhu G, Montgomery GW, James MR, Trent JM, (A flat seborrheic keratosis may be also taken Hayward NK, Martin NG, Duffy DL. A genome- into differential diagnosis, but early seborrheic wide scan for naevus count: linkage to CDKN2A keratoses, as a rule, tend to have more dull col- and to other chromosome regions. Eur J Hum Gen- ors and a finely stippled surface.) et 2007;15:94–102 2. Zalaudek I, Grinschgl S, Argenziano G, Marghoob AA, Blum A, Richtig E, Wolf IH, Fink-Puches R, Kerl H, Soyer HP, Hofmann-Wellenhof R. Age-related Performed management prevalence of dermoscopy patterns in acquired melanocytic naevi. Br J Dermatol 2006;154:299–304 No further treatment was necessary. Common Nevus Chapter III.7 105

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