Dermoscopic Criteria, Patient Factors May Help Manage Pigmented Melanocytic Nevi

Laurie Barclay, MD

September 03, 2009

September 3, 2009 — Dermoscopic criteria and patient-related factors, summarized by a 4 x 4 x 6 "rule," may help clinicians manage pigmented melanocytic nevi, according to the results of a review reported in the August issue of Archives of Dermatology.

"By allowing visualization of submacroscopic pigmented structures that correlate with specific underlying histopathologic structures, dermoscopy provides a more powerful tool than the naked-eye examination for clinicians to determine the need to excise a lesion," write Iris Zalaudek, MD, from Medical University of Graz in Graz, Austria, and colleagues. "Recent dermoscopy studies provide new understanding of factors that influence nevus pattern and offer intriguing insights into nevogenesis. Herein, we present a synopsis of the most common dermoscopic patterns associated with nevi and the factors influencing the nevus pattern in a given individual, and we discuss some of the recent concepts of nevogenesis."

The reviewers searched Medline and Journals@Ovid for English-language and German-language publications from 1950 to January 2009, without exclusion criteria, using search terms of dermoscopy, dermatoscopy, epiluminescence microscopy (ELM), surface microscopy, digital dermoscopy, digital dermatoscopy, digital epiluminescence microscopy, digital surface microscopy, melanocytic skin lesion, nevi, and pigmented skin lesions.

Criteria for Diagnosis

Four criteria, each of which is characterized by 4 variables, can assist in the dermoscopic diagnosis of nevi: (1) color (black, brown, gray, or blue); (2) pattern (globular, reticular, starburst, or homogeneous blue); (3) pigment distribution (multifocal, central, eccentric, or uniform); and (4) special sites (face, acral areas, nail, or mucosa).

A combination of blue and/or gray and white suggests regression, which may occur in melanoma and should therefore raise the index of suspicion, especially when a lesion shows regression features over more than 10% of the lesion surface. Although evaluation of color alone is insufficient to rule out melanoma, the basic rule "the more colors, the more suspect" is helpful for identifying atypical melanocytic proliferations.

Because the architecture and pigment distribution of atypical melanocytic proliferations are usually much more asymmetric than those of common nevi, another helpful algorithm is "the more colors, the more structures, the more suspect." The probability of a lesion being melanoma is higher when it has eccentric hyperpigmentation or multifocal pigmentation, and conventional wisdom is that these lesions should be closely monitored or excised.

However, a very recent study showed that 92% of all melanomas with eccentric hyperpigmentation or multifocal pigmentation had additional melanoma-specific dermoscopic features allowing the correct diagnosis regardless of the pigment distribution, and that all lesions with eccentric hyperpigmentation but lacking melanoma-specific features were benign.

Nevus-associated melanomas tend to be more common on axial body sites, particularly the lower extremities. Histopathologic analysis usually reveals that the associated nevus component has a congenital-like pattern with dermal involvement. Because the risk for malignant transformation is low for small congenital or congenital-like nevi, systematic excision of these common nevi is not indicated.

Patient-Related Factors and Pigmentation Pattern

There are also 6 patient-related factors that may affect the pattern of pigmentation of the individual nevi: age, skin type, history of melanoma, ultraviolet (UV) exposure, pregnancy, and growth dynamics.

"The 4 x 4 x 6 'rule' may help clinicians remember the basic dermoscopic criteria of nevi and the patient-related factors influencing their patterns," the study authors write. "Dermoscopy is a useful technique for diagnosing melanocytic nevi, but the clinician should take additional factors into consideration to optimize the management of cases of pigmented lesions."

The effects of specific patient-related factors on dermoscopic patterns are as follows:

  • Age-Related Nevus Pattern: Most nevi in prepubertal children have a globular or homogeneous pattern. In contrast, the reticular (network) pattern is most frequently observed in adults. Globular nevi are more often located on the head, neck, and upper trunk, whereas reticular nevi occur in any areas of the trunk and extremities.

  • Skin Type–Related Nevus Pattern: Individuals with skin type I (very fair skin, red hair) have a predominant nevus type characterized by light brown color and central hypopigmentation. Nevi in patients with skin types II (light skin, blond hair) and III (medium skin tone, brown hair) tend to be light to dark brown with multifocal pigmentation. Nevi of skin type IV (dark skin, black hair) can be black or hypermelanotic nevi and are typically dark brown with central hyperpigmentation.

  • Melanoma-Related Nevus Pattern: Patients with melanoma more often have mixed pattern nevi (reticular-globular pattern or homogeneous-globular pattern), whereas healthy individuals are more likely to have a more uniform pattern.

  • UV-Related Nevus Pattern: After UV exposure, nevi may develop reversible changes of dermoscopic features, such as pigmentation darkening; pigment network fading; increased size; erythema; and new formation of irregular dots, globules, or blotches.

  • Pregnancy-Related Nevus Pattern: Reversible changes in nevi during pregnancy may include lightening or darkening, progressive reduction in thickness and prominence of reticular pattern, new appearance of dots or globules, increased vascularization, and increase in size, particularly on the abdomen.

  • Growth Dynamics: Evolving nevi, which are characterized on dermoscopic examination by a peripheral rim of small brown globules, first appear in pubescent adolescents and continue developing through the second decade of life. Follow-up of these nevi with digital dermoscopy shows symmetric enlargement, disappearance of peripheral globules, and stabilization of lesion size.

Spitz and Reed Nevi

Depending on the growth phase of the lesion, so-called Spitz and Reed nevi may show different patterns: globular at first, then the classic starburst pattern, then finally the homogeneous pattern. Some Spitz and Reed nevi may even completely disappear. In contrast, homogeneous blue nevi appear to be highly stable lesions. Excision of all spitzoid lesions, particularly in adults, is always recommended because no single criterion is sufficiently accurate to differentiate spitzoid-appearing melanomas from Spitz and Reed nevi.

When examining individuals with multiple nevi, the clinician should first identify the patient's predominant nevus pattern, defined as the pattern seen in more than 30% of all nevi. This allows the identification of atypical lesions that deviate from the predominant pattern.

"Using the dermoscopic 4 x 4 patterns of pigmented nevi and the 6 factors influencing the individual's nevus pattern might be considered a guide to help the clinician in diagnosing pigmented nevi and managing cases of multiple melanocytic nevi," the review authors conclude. "While most of the dermoscopic patterns of nevi have been well investigated, only partial evidence exists on the individual or environmental factors that influence the patterns of a single nevus or a predominant nevus type. Studies focusing on the individual and the environmental influences on dermoscopic nevus patterns are needed in the future to better understand the role of these factors in the identification of atypical melanocytic skin tumors."

Limitations of the review are that the overwhelming majority of the identified articles were prospective or retrospective observational studies from single institutions or multicenter collaborating groups, and the quality of the evidence supporting screening recommendations was most often level B.

The Elise Richter Program of the Austrian Science Fund supported this review. The review authors have disclosed no relevant financial relationships.

Arch Dermatol. 2009;145:816-826.Abstract


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