Dysplastic / Atypical nevi
The concept of dysplastic nevi Dysplastic (atypical) nevi (DN) (Tucker et al., 1997) are benign acquired melanocytic neoplasms that clinically resemble melanoma since they frequently share some or all of the clinical ABCDE (A, asymmetry; B, border irregularity; C, color variability; D, diameter >6 mm; E, evolving) morphologic features of melanoma. The significance of DN is that individuals with such atypical moles are at significant increased risk of developing melanoma (Tucker et al., 1997) independent of the total number of nevi present (Bevona et al., 2003; Roesch et al., 2006). Although most melanomas developing in individuals with DN arise de novo, between 25 and 40% develop in contiguity with a DN, leading to the hypothesis that certain DN may be nonobligate precursors to a subset of melanomas (Bevona et al., 2003). The goal of the clinical evaluation and management of patients who present with DN is to excise those DN that have given rise to melanoma and to determine which newly developing lesions and/or changing melanocytic neoplasms should be biopsied and which can be safely monitored. In this clinical decision-making process, dermoscopy has proved to be extremely valuable (Roesch et al., 2006). Since DN far outnumber melanomas and since patients with the DN phenotype often have many nevi and intermittently develop new nevi, the continuous prophylactic excision of all DN is an impractical management strategy. Experience has shown that the combined use of patient history, total cutaneous examination, dermoscopy, utilizing the comparative approach (Argenziano et al., 2011) sequential imaging of suspicious (but lacking definitive criteria for melanoma) lesions, and lifelong followup is an effective approach at detecting early curable melanomas, while limiting the number of unnecessary biopsies of biologically stable lesions. For select patients total cutaneous photographs coupled with short-term (three months) dermoscopic mole monitoring can greatly assist the clinician in detecting biologically relevant lesions, such as curable de novo melanomas and melanomas arising from pre-existing melanocytic nevi and perhaps even lesions that may be destined to become melanoma (i.e., severely atypical nevi that are changing) (Altamura et al., 2008; Menzies et al., 2001; Kittler et al., 2006). It is currently assumed that all DN are acquired melanocytic neoplasms and as such all DN will appear as new lesions. These lesions will progressively change until they enter senescence. These senescent DN are in fact stable lesions (Tucker et al., 2002). With that being said, it should come as no surprise that the vast majority of new or changing melanocytic lesions are DN and not melanoma (Fuller et al., 2007; Kittler et al., 2000; Banky et al., 2005). Since change is a sensitive indicator of melanoma, two important questions need to be addressed when confronted with a new or changing lesion: “Is the atypical melanocytic lesion a melanoma or is it the much more common dysplastic nevus?” and “Can the lesion be monitored or should it be biopsied?”. To this end, better appreciation of primary morphology of the lesion in question may help determine which lesion requires biopsy. The clinical ABCD acronym cannot be expected to distinguish melanoma from DN because both lesions, by definition, share the same features clinically. However, dermoscopy often, but not always, can distinguish malignant from benign melanocytic lesions that are clinically indeterminate by the naked eye. Specific dermoscopic structures and patterns can aid in the decision as to which lesions can be followed and which lesions require biopsy. the role of dermoscopy in assessing atypical melanocytic neoplasms It is important to emphasize that most DN are rather stable lesions, whereas melanomas are generally changing (e.g., biologically dynamic) lesions. Furthermore, despite their ABCD clinical features, the vast majority of DN can be diagnosed dermoscopically as benign melanocytic neoplasms by experienced dermoscopists. Such lesions do not have to be biopsied but can be followed, thus avoiding unnecessary surgery and reducing the cost of medical care. On the other hand, a significantly changing lesion could be biologically relevant since it may be a melanoma or a true melanoma precursor. Such lesions are generally best biopsied Different score-based dermoscopy algorithms (e.g., ABCD, Menzies, seven-point checklist, CASH) have been developed to assist clinicians in distinguishing DN from melanoma (Stolz et al., 1994; Menzies, 2009; Argenziano et al., 1998). Many DN that are clinically suspicious for melanoma can be correctly identified as benign using such dermoscopy algorithms. Yet, there still remains a significant portion of DN that score in the “suspicious” range implying the algorithm cannot distinguish these DN from melanoma with assurance. This is due to the considerable overlap in the primary morphology between DN and melanoma not only clinically but also dermoscopically. Pattern analysis, the most frequent method used by experienced dermoscopists, has been shown to better discriminate between many DN and melanomas as compared with other scoring algorithms (Argenziano et al., 2003). Pattern analysis involves determining the overall (global) dermoscopic pattern based on the presence or absence of network, globules, homogenous (structureless) areas, and identifying the presence or absence of specific local features. In evaluating patterns, the observer must consider not only the overall dermoscopic pattern, but also the number and distribution of colors and structures, whether the dermoscopic structures are “regular” or “irregular” (see chap. 6a for further details), and whether the colors and structures are distributed symmetrically or asymmetrically and in an organized or disorganized manner. dermoscopic patterns of dysplastic nevi The global patterns of melanocytic nevi used for classification are reticular, globular, homogenous, reticular–globular, reticular–homogenous, globular–homogenous, and two components (Hofmann-Wellenhof et al., 2001; Blum et al., 2003). Benign melanocytic nevi often present with one of the well-recognized symmetric and organized patterns listed in and depicted schematically in. In addition, it is not uncommon to encounter dysplastic with a multicomponent pattern By definition, lesions with a multicomponent pattern must possess three or more of the following structures: globules, reticulation, blotches, dots, veil, regression structures, and/or structureless areas. Melanoma usually enters the differential diagnosis of lesions manifesting a multicomponent pattern. The reticular type dysplastic nevus presents with a pigmented network. The “lines” of the network represent pigmented melanocytes/ nevus cells and melanized keratinocytes in or along the epidermal rete ridges. The “holes” are created by the relative paucity of pigment overlying the suprapapillary epidermal plate overlying the dermal papilla. Benign patterns include network diffusely distributed throughout the lesion and network scattered in patches throughout the lesion. Within the benign spectrum of reticular DN, pigmentation may also vary depending on the patient’s phenotype. In fair skin there will often be a central area of hypopigmentation (often structureless) and in darker skin there will be a central area of hyperpigmentation or blotch (obscuring the network). These are considered reticular–homogenous DN. The globular type DN prominently features globules, which represent nevocytic nests of melanocytes. Benign patterns include globules distributed evenly throughout the lesion and the globular–homogenous pattern, which has structureless areas distributions within the lesion. The homogenous type DN is distinguished by its predominant lack of structures. Although a few globules and/or network fragments may be found focally, the overall pattern and pigmentation is homogenous. We have observed through confocal microscopy and histology that homogenous DN morphologically may be junctional, compound, or intradermal nevi. Reticular–globular DN display a combination of aforementioned features seen in reticular and globular DN. Common benign patterns include central globules with peripheral network and central network or homogenous areas with brown globules located at the periphery. The peripheral globules, usually corresponding to junctional nevomelanocytic nests at the tips of rete ridges, are frequently encountered in nevi undergoing enlargement (i.e., growing nevi). Starburst pattern is a specific pattern commonly seen in Spitz nevi. The starburst pattern can manifest with peripheral globules tiered one on top of the other or with steaks around the entire perimeter. The starburst pattern with peripheral streaks is quite specific for the diagnosis of Spitz nevus. Although the starburst pattern with peripheral tiered globules is commonly seen in Spitz nevi, it can also be seen in dysplastic nevi with spitzoid features. Two component nevi reveal two different patterns (reticular–globular, reticular–homogenous, or globular–homogenous). One half of the lesion manifests one pattern while the other half of the lesion manifests a different pattern. Multicomponent DN have three or more patterns, including reticular, globular, and homogenous areas. The homogenous areas include blotches, which by definition are hyperpigmented, and structureless areas, which by definition are hypopigmented areas (NB: depigmented scar-like areas are not classified as structureless hypopigmented areas but rather as areas with regression). An alternative definition of a “multicomponent pattern” is a lesion that has three or more of the following structures: network, streaks, negative pigment network, chrysalis, dots, globules, blotches, structureless areas, and blue-white structures. If these structures are distributed symmetrically (at least in one axis) and in an organized manner, the lesion will usually prove to be a dysplastic nevus on biopsy However, if distributed asymmetrically, or in a disorganized manner then the diagnosis of melanoma must be considered understanding dysplastic nevi can share the same dermoscopic features of melanoma and, therein lies the knotty problem of their differentiation
Indeterminate dysplastic nevi dermoscopic patterns
Familiarity with the dermoscopic patterns exhibited by melanocytic nevi, which typically demonstrate symmetry of pattern, structures, and colors, assists in distinguishing benign from malignant melanocytic lesions. Identification of these benign dermoscopic patterns in a lesion that appears suspicious to the naked eye usually will alleviate concerns for melanoma and directs the management toward conservative clinical followup Although dermoscopy allows many DN to be correctly identified as benign, even dermoscopy experts are challenged by a subset of indeterminate DN (i.e., multicomponent pattern) that are difficult, if not impossible, to differentiate from melanoma. Excisional biopsy or shortterm mole monitoring (i.e., short-term mole monitoring criteria include melanocytic lesions without evidence of melanoma, moderately atypical, flat or slightly raised lesions without a history of change, or mildly atypical lesions with a history of change) is recommended for most of such melanoma mimicking lesions. Although short-term mole monitoring can greatly increase specifi ity, this technique should never be employed in monitoring indeterminate nodular lesions. Such lesions should be biopsied without delay since even modest delays in the diagnosis of nodular melanoma can have deleterious consequences. With that said, with experience, the vast majority of DN can be recognized as benign lesions that do not have to be biopsied, but even such nevi should be followed by periodic patient self-examination and periodic physician-based examination remembering that these patients are at increased risk for developing melanoma and melanomas may on occasion arise in association with atypical nevi. As stated above, recognition of the commonly encountered benign dermoscopic patterns of melanocytic neoplasms can help in the evaluation of clinically suspected lesions. However, some benign nevi may deviate from these well-defined dermoscopic patterns or reveal melanoma-specific structures as listed in. Lesions with atypical structures or any variation from the symmetry and even distribution of colors and structures associated with benign patterns should be viewed with caution. An important approach to the differentiation of melanoma from DN is the degree of architectural order versus disorder present in the lesion. Another important component of the analysis is the fi ndings revealed by careful medical history, especially including the evolution (change) and symptomatology (especially pruritus, pain, formication, spontaneous crusting, or bleeding) of the lesion. In general, if the lesion manifests one of the benign patterns and have none of the melanoma-specific structures listed in then the lesion can be considered benign. If the lesion manifests an overall benign pattern, but also has one of the melanoma-specific structures listed in then the lesion should be biopsied or subjected to short-term mole monitoring. The decision to biopsy or monitor will be greatly influenced by whether or not the lesion is a dermoscopic outlier lesion, whether or not it manifests a pattern similar to neighboring nevi and whether or not it is palpable (nodular). For lesions that do not manifest one of the benign nevus patterns while at the same time revealing at least one of the melanoma-specific structures listed in, a biopsy should be strongly considered to rule out melanoma. Lastly, if the lesion does not adhere to one of the benign nevus patterns and has no melanoma-specifi c structures then the lesion can be monitored or biopsied. The decision to biopsy or monitor will be greatly influenced by whether or not the lesion is a dermoscopic outlier lesion (appears different compared with surrounding nevi), whether or not it manifests a pattern similar to neighboring nevi and whether or not it is palpable (nodular). Based on the aforementioned management outline it should be clear that the principal management decision with indeterminate lesions is excisional biopsy versus short-term monitoring. Although the decision to biopsy or monitor will be influenced greatly by whether or not the lesion is a dermoscopic outlier lesion, whether or not it manifests a pattern similar to neighboring nevi and whether or not it is palpable (nodular), the decision will also be infl uenced by the physician’s experience; the patient’s history with regard to the lesion (i.e., the physician should not dismiss a patient that insists the lesion should be removed); the patient’s total mole count (i.e., the threshold for excision is lower in a patient with a single atypical lesion than in a patient floridly expressing DN); the availability of the total-cutaneous photographs and/or sequential digital monitoring; and the anticipated patient compliance with followup (Argenziano et al., 2008). Although distinguishing between some DN and melanoma can be difficult, there is reason for optimism. The development of new criteria may improve the differentiation of indeterminate lesions, which in turn may shrink the subset of lesions subjected to biopsy. Current studies are also considering the use of polarized versus nonpolarized light dermoscopy; confocal microscopy; automated (classifi cation by “computer vision” analysis); and other new emerging technologies to help in this endeavor. Also, the advent of teledermoscopy is upon us by which high-quality dermoscopic images can be instantly sent worldwide by Internet to expert dermoscopists who are able to render their interpretations of diffi cult lesions and assist in the therapeutic management decisions.
This chapter was adapted from Marghoob et al. [1]
Reticular diffuse
Diffuse network with uniform thickness and color of lines. The holes of the network are of relatively
uniform size. The network tends to fade at the periphery. This pattern can be seen in congenital nevi,
especially those located on the lower extremity, and in acquired nevi
Reticular patchy
Network with uniform thickness and color of lines. However, the network is not contiguous due to the presence of intervening homogenous structureless areas. This pattern can be seen in congenital nevi, especially those located on the lower extremity, and in acquired nevi
Peripheral reticular with central hypopigmentation
A relatively uniform network at the periphery of the lesion with a central homogenous and hypopigmented, but not depigmented, structureless area. This type of acquired nevus is more common in fair skin phenotypes
Peripheral reticular with central hyperpigmentation
A relatively uniform network at the periphery of the lesion with a central homogenous and hyperpigmented
blotch. This type of acquired nevus is more common in darker skin phenotypes. The blotch can
often be removed or lightened by tape stripping
Globular
Globules of similar shape, size, and color distributed symmetrically throughout the lesion. This pattern is
seen most commonly in congenital nevi
Peripheral reticular with central globules
A relatively uniform network at the periphery of the lesion with multiple globules in the center. Nevi with
this pattern often have histopathology features suggestive that the nevus has a congenital origin
Peripheral globules with central network or homogeneous area
The central component of this type of nevus is either reticular or homogenous. Relatively uniform globules
surround the entire perimeter of the lesion. This pattern is suggestive of an acquired growing nevus that
has not yet undergone senescence
Starburst
Streaks (radial streaming or pseudopods) present around the perimeter of the lesion giving the appearance
of an exploding star. The starburst pattern can also manifest with peripheral globules that are tiered one
on top of the other
Homogenous tan, brown, or blue pigmentation
Primarily diffuse structureless pattern with or without the presence of small foci of reticular network,
network fragments, and/or globules. When tan in color they usually represent acquired nevi in fair skin
phenotypes. When darker brown in color they usually represent congenital nevi. When blue in color they
represent blue nevi
Two component
These lesions reveal two different patterns (reticular–globular, reticular–homogenous, or globular–
homogenous). A half of the lesion manifests one pattern, whereas the other half of the lesion manifests
a different pattern
- ↑ An Atlas of Dermoscopy, Second Edition. Marghoob A. et al. CRC Press; 2012.
