My approach to atypical melanocytic lesions

Dysplastic nevus part I: Historical perspective, classification, and epidemiology

Since the late 1970s, the diagnosis and management of dysplastic nevi have been areas fraught with controversy in the fields of dermatology and dermatopathology. Diagnostic uncertainty and lack of standardized nomenclature continue to propagate confusion among clinicians, dermatopathologists, and patients. In part I of this CME review article, we summarize the historical context that gave rise to the debate surrounding dysplastic nevi and review key features for diagnosis, classification, and management, as well as epidemiology. We discuss essentials of clinical criteria, dermoscopic features, histopathologic features, and the diagnostic utility of total body photography and reflectance confocal microscopy in evaluating dysplastic nevi, with emphasis on information available since the last comprehensive review a decade ago.

Recurrence of Dysplastic Nevi Is Strongly Associated with Extension of the Lesions to the Lateral Margins and into the Deep Margins through the Hair Follicles in the Original Shave Removal Specimens

Melanocytic nevi, including dysplastic or atypical nevi (DN), can recur or persist following shave removal procedures, and recurrence may resemble melanoma, both clinically and histologically (pseudomelanoma). Recurrence may originate from proliferation of the remaining neoplastic melanocytes following incomplete removal. The present study determines the rate and etiology of this event. A cross-sectional analysis of 110 excision specimens showing histological recurrence was performed, and these specimens were compared to the slides of the original shave specimens showing mildly atypical DN. In the second portion of the study, a retrospective review of 167 cases with biopsy-proven mildly atypical DN which were followed up for at least two years was conducted to determine the rate of recurrence/persistence. When followed up for two years, DN, with positive shave margins, defined by extension or very close extension (≤0.2 mm) of the lesions to the lateral margins and into the deep margins through the hair follicles in the shave removal specimens, have a higher probability of recurrence than DN with negative (or clear) margins (odds ratio (OR) = 158; 95% confidence interval (CI) = 36.62–683; P < 0.001). The overall rate of histologically confirmed recurrence/persistence was approximately 10%.

Dysplastic (or Atypical) Nevi Showing Moderate or Severe Atypia With Clear Margins on the Shave Removal Specimens Are Most Likely Completely Excised

BACKGROUND

Dysplastic nevi (DN) are graded by their degree of atypia into 3 categories of mild, moderate, and severe. In many practices, DN with moderate or severe atypia are generally excised regardless of the status of the shave specimen margins.

OBJECTIVE

With a new approach toward the margins on the shave removal specimens (SRS), the goal herein is to assess whether the shave removal procedure can sufficiently remove DN with moderate or severe atypia.

METHODS

A total of 426 SRS diagnosed with DN showing moderate or severe atypia between January and December 2015 along with their post-shave excision specimens were reviewed. Based on the author's experience, clear or negative margins on the SRS were defined as neoplastic melanocytes confined within >0.2 mm of the lateral and deep specimen margins. The biopsy specimens were accompanied by Melan-A highlighting the subtle neoplastic cells.

RESULTS

With a negative predictive value (NPV) of 98.4% (confidence interval: 97.2% to 100%, P < .001), DN showing moderate or severe atypia with clear margins are most likely removed by the shave procedure.

CONCLUSION

Routine excision of DN showing moderate or severe atypia with clear margins on SRS is not necessary. Regular surveillance is sufficient.

Selected benign cutaneous lesions that may simulate melanoma histologically

As cutaneous melanomas manifest a wide spectrum of clinical and pathologic presentations, several other lesions enter into their differential diagnosis. This article considers those entities, including melanocytic hyperplasia, cellular nodules in congenital nevi, atypical lentiginous melanocytic proliferations, "special site" nevi, epithelioid histiocytoma, neurothekeoma, cellular schwannoma, and proliferating scars.

Case reports of fatal or metastasizing melanoma in children and adolescents: a systematic analysis of the literature

Childhood melanoma (ChM) is rare, with clinical and epidemiologic characteristics that differ from those of adult melanomas. The objective of the current study was to systematically identify and analyze case reports and case series of fatal and metastasizing ChM in the medical literature. ChM case reports with a fatal outcome or metastases were identified using a Medline search and subdivided into ChM developing in the absence of a congenital melanocytic nevus (ChM without CMN) and ChM associated with a CMN (ChM with CMN); 258 cases of ChM without CMN (206 cutaneous, 52 noncutaneous) were identified. In cutaneous ChM without CMN with a fatal outcome (n = 155), the mean age at diagnosis was 13.1 years (median 14 yrs). The mean Breslow index in this group was 8.5 mm for children ages 0 to 10 years and 3.7 mm for children ages 11 to 18 years. In ChM with CMN (n = 178; 112 cutaneous, 66 central nervous system [CNS]), the mean age at diagnosis was 5.8 years for cutaneous melanoma (median 3 yrs) and 5.5 years for CMN-associated CNS melanoma (median 3 yrs). The majority of CMN-associated cutaneous melanomas developed in small and giant CMN (vs medium and large); 53.9% of CNS melanomas developed in patients with multiple medium CMN. This study represents the largest and most complete synopsis of ChM case reports in the medical literature. Our analysis supports the view that cutaneous ChM without CMN (or associated with smaller CMN) differs in several important aspects from ChM associated with large or giant CMN.

Nevomelanocytic atypia detection by in vivo reflectance confocal microscopy

BACKGROUND AND OBJECTIVE

In vivo reflectance confocal microscopy (RCM) is a promising novel technology for non-invasive early diagnostics of cutaneous melanoma. However, the possibility to detect melanocytic atypia in nevi by means of in vivo RCM remains unknown. The aim of the study was to evaluate the significance of in vivo RCM features of melanocytic atypia for the diagnosis of melanocytic nevi, dysplastic nevi and cutaneous melanoma.

MATERIALS AND METHODS

A total of 138 melanocytic skin lesions comprising 25 melanocytic nevi, 69 dysplastic nevi and 44 melanomas were analyzed by means of dermoscopy, in vivo RCM and routine histopathology. In vivo RCM images were analyzed for the arrangement of keratinocytes in epidermis, pagetoid cells and junctional melanocytic nests and correlated refractivity aspects of nests with histopathology.

RESULTS

Separately and all together taken the in vivo RCM features of melanocytic atypia were significant in differential diagnosis of benign and malignant melanocytic skin lesions, though none of the features was significant in discriminating nevi without cytologic atypia of dysplastic nevi. In vivo RCM feature of dense cell clusters corresponded with melanin containing nevomelanocytes on histopathology though exact correspondence of non-homogeneous and atypical sparse cell clusters remained questionable.

CONCLUSIONS

Nevus with histopathologically confirmed nevomelanocytic atypia (dysplastic nevus) could not be distinguished from nevus without atypia using analyzed in vivo RCM features of melanocytic atypia. More accurate diagnostics by means of in vivo RCM needs further investigation on reflectance of single and nested cutaneous melanocytes in benign and malignant skin lesions.

Distinguishing between benign and malignant melanocytic nevi by in vivo multiphoton microscopy

Monitoring of atypical nevi is an important step in early detection of melanoma, a clinical imperative in preventing the disease progression. Current standard diagnosis is based on biopsy and histopathologic examination, a method that is invasive and highly dependent upon physician experience. In this work, we used a clinical multiphoton microscope to image in vivo and noninvasively melanocytic nevi at three different stages: common nevi without dysplastic changes, dysplastic nevi with structural and architectural atypia, and melanoma. We analyzed multiphoton microscopy (MPM) images corresponding to 15 lesions (five in each group) both qualitatively and quantitatively. For the qualitative analysis, we identified the morphologic features characteristic of each group. MPM images corresponding to dysplastic nevi and melanoma were compared with standard histopathology to determine correlations between tissue constituents and morphology and to evaluate whether standard histopathology criteria can be identified in the MPM images. Prominent qualitative correlations included the morphology of epidermal keratinocytes, the appearance of nests of nevus cells surrounded by collagen fibers, and the structure of the epidermal-dermal junction. For the quantitative analysis, we defined a numerical multiphoton melanoma index (MMI) based on three-dimensional in vivo image analysis that scores signals derived from two-photon excited fluorescence, second harmonic generation, and melanocyte morphology features on a continuous 9-point scale. Indices corresponding to common nevi (0-1), dysplastic nevi (1-4), and melanoma (5-8) were significantly different (P < 0.05), suggesting the potential of the method to distinguish between melanocytic nevi in vivo.

Optimal management of common acquired melanocytic nevi (moles): current perspectives

Although common acquired melanocytic nevi are largely benign, they are probably one of the most common indications for cosmetic surgery encountered by dermatologists. With recent advances, noninvasive tools can largely determine the potential for malignancy, although they cannot supplant histology. Although surgical shave excision with its myriad modifications has been in vogue for decades, the lack of an adequate histological sample, the largely blind nature of the procedure, and the possibility of recurrence are persisting issues. Pigment-specific lasers were initially used in the Q-switched mode, which was based on the thermal relaxation time of the melanocyte (size 7 μm; 1 μsec), which is not the primary target in melanocytic nevus. The cluster of nevus cells (100 μm) probably lends itself to treatment with a millisecond laser rather than a nanosecond laser. Thus, normal mode pigment-specific lasers and pulsed ablative lasers (CO2/erbium [Er]:yttrium aluminum garnet [YAG]) are more suited to treat acquired melanocytic nevi. The complexities of treating this disorder can be overcome by following a structured approach by using lasers that achieve the appropriate depth to treat the three subtypes of nevi: junctional, compound, and dermal. Thus, junctional nevi respond to Q-switched/normal mode pigment lasers, where for the compound and dermal nevi, pulsed ablative laser (CO2/Er:YAG) may be needed. If surgical excision is employed, a wide margin and proper depth must be ensured, which is skill dependent. A lifelong follow-up for recurrence and melanoma is warranted in predisposed individuals, although melanoma is decidedly uncommon in most acquired melanocytic nevi, even though histological markers may be seen on evaluation.

Outcomes of biopsies and excisions of dysplastic acral nevi: a study of 187 lesions

BACKGROUND

Despite their frequency in clinical practice, controversy exists regarding the significance and management of dysplastic nevi (DN). Although the perception of DN as precursors to melanoma is questionable, excisions of biopsy-proven DN are commonplace in clinical practice. The management of dysplastic acral nevi is of interest given the challenge of surgery at acral sites.

OBJECTIVE

To determine the outcomes of biopsies of clinically atypical acral nevi and excisions of histologically dysplastic acral nevi (HDN).

MATERIALS AND METHODS

Retrospective review of consecutive patients at a private dermatology practice who had a biopsy of an atypical acral nevus from December 2004 to July 2012.

RESULTS

One hundred eighty-seven atypical acral nevi were biopsied from 168 patients (77 (41%) HDN, 108 (58%) common nevi). Based on initial histology, 30 (39%) HDN were recommended for excision and eight (10%) for clinical observation. Twenty-seven of the 77 HDN were excised; 23 (85%) revealed scar only, and four (15%) revealed residual DN not involving the margin.

CONCLUSION

Routine excision of biopsy-proven dysplastic acral nevi may not be necessary.

Image and statistical analysis of melanocytic histology

AIMS

We applied digital image analysis techniques to study selected types of melanocytic lesions.

METHODS AND RESULTS

We used advanced digital image analysis to compare melanocytic lesions as follows: (i) melanoma to nevi, (ii) melanoma subtypes to nevi, (iii) severely dysplastic nevi to other nevi and (iv) melanoma to severely dysplastic nevi. We were successful in differentiating melanoma from nevi [receiver operating characteristic area (ROC) 0.95] using image-derived features, among which those related to nuclear size and shape and distance between nuclei were most important. Dividing melanoma into subtypes, even greater separation was obtained (ROC area 0.98 for superficial spreading melanoma; 0.95 for lentigo maligna melanoma; and 0.99 for unclassified). Severely dysplastic nevi were best differentiated from conventional and mildly dysplastic nevi by differences in cellular staining qualities (ROC area 0.84). We found that melanomas were separated from severely dysplastic nevi by features related to shape and staining qualities (ROC area 0.95). All comparisons were statistically significant (P < 0.0001).

CONCLUSIONS

We offer a unique perspective into the evaluation of melanocytic lesions and demonstrate a technological application with increasing prevalence, and with potential use as an adjunct to traditional diagnosis in the future.

Atypical genital nevus

CONTEXT

Atypical genital nevus is rare and the only poorly documented melanocytic lesion in the spectrum of nevi of special sites. It is characterized by unique and reproducible histologic features, which may appear alarming and may raise significant concern for a diagnosis of melanoma.

OBJECTIVES

To present the clinical and histologic features of atypical genital nevus with emphasis on distinction from vulvar melanoma.

DATA SOURCES

The findings are based on a review of the current literature.

CONCLUSIONS

Atypical genital nevus is most often found in the vulva of premenopausal women. Despite the alarming histologic features, its clinical behavior appears benign with only rare local recurrence after incomplete removal. Recognition of this unusual melanocytic lesion and its characteristic histologic features is important to avoid overdiagnosis of invasive melanoma, with subsequent wide excision or sentinel lymph node biopsy, especially in view of the sensitive anatomic location.

Frequent mitotic activity in banal melanocytic nevi uncovered by immunohistochemical analysis

The presence and distribution of mitotic figures is an important discriminatory parameter in the assessment of melanocytic lesions. We evaluated the number and distribution of mitotic figures in 353 randomly collected melanocytic nevi of various subtypes by hematoxylin and eosin (H&E) staining and immunohistochemically with the 2 mitotic markers Phospho-Histone H3 Ser28 (PHH3) and MPM2. At least 1 mitotic figure was present in 19.5%, 31.3%, and 42.8% of H&E-, PHH3-, and MPM2-stained lesions, respectively. In common compound nevi, the mean number of dermal mitoses amounted to 0.024/mm dermal surface area in the H&E staining (PHH3: 0.061; MPM2: 0.087) and to 0.175/mm in Spitz nevi (PHH3: 0.325; MPM2: 0.45). Nevi exhibiting mitotic figures were significantly more frequent in the youngest age group (0-20 years) than in patients older than 50 years (P < 0.0001). In the upper half of the dermis, mitotic activity was roughly 3 times as frequent as compared with the lower half. Clusters of mitotic figures within the dermis were not observed. Mitotic activity in obviously benign melanocytic nevi is not rare even in the deep dermal part. More than 2 mitotic figures per lesion can usually be explained either by the nevus subtype, young patient age, traumatization, or inflammation. PHH3 and MPM2 are a valuable diagnostic adjunct in the evaluation of melanocytic tumors allowing more sensitive and faster recognition of mitotic figures and their distribution.

Spindle cell melanocytic lesions--part I: an approach to compound naevoidal pattern lesions with spindle cell morphology and Spitzoid pattern lesions

Melanocytic lesions show great morphological diversity in their architecture and the cytomorphological appearance of their composite cells. Whereas functional melanocytes reveal a dendritic cytomorphology and territorial isolation, lesional naevomelanocytes and melanoma cells typically show epithelioid, spindled or mixed cytomorphologies and a range of architectural arrangements. Spindling is common to melanocytic lesions, and may be either a characteristic feature or a divergent appearance. The presence of spindle cells may mask the melanocytic nature of a lesion, and is often disconcerting, either because of its infrequent appearance in a particular lesion or its interpretation as a dedifferentiated phenotype. Spindle cell melanocytic lesions follow the full spectrum of potential biological outcomes, and difficulty may be experienced judging the nature of a lesion because of a lack of consistently reliable features to predict biological behaviour. Over time, recognition of numerous histomorphological features that may portend a more aggressive lesion have been identified. However, the translation of these features into a diagnostic entity requires a gestalt approach. Although most spindle cell melanocytic lesions can reliably be resolved with this standard approach, problem areas do exist and cause no end of grief to the surgical pathologist or dermatopathologist. In this review, the authors present their algorithmic approach to spindle cell melanocytic lesions and discuss each entity in turn, in order to (1) model a systematic approach to such lesions, and (2) provide familiarity with those melanocytic lesions that either typically or occasionally display a spindled cytomorphology.

Low rates of clinical recurrence after biopsy of benign to moderately dysplastic melanocytic nevi

BACKGROUND

Little is known about the recurrence/persistence rates of dysplastic nevi (DN) after biopsy, and whether incompletely removed DN should be re-excised to prevent recurrence.

OBJECTIVE

Our purpose was to determine the recurrence rates of previously biopsied DN, and to assess whether biopsy method, margin involvement, congenital features, epidermal location, and degree of dysplasia are associated with recurrence.

METHODS

Patients having a history of a "nevus biopsy" at least 2 years earlier were assessed for clinical recurrence. Slides of original lesions were re-reviewed by a dermatopathologist.

RESULTS

A total of 271 nevus biopsy sites were assessed in 115 patients. Of 195 DN with greater than 2 years of follow-up, 7 (3.6%) demonstrated recurrence on clinical examination. In all, 98 DN had a follow-up period of at least 4 years with no clinical recurrence. Of 61 benign nevus biopsy sites examined, clinical recurrence was observed in two (3.3%). For all nevi, recurrence was significantly associated with shave biopsy technique but not with nevus dysplasia or subtype, or the presence of positive margin or congenital features.

LIMITATIONS

Most biopsies were performed in a pigmented lesion clinic at a single tertiary referral center. Determinations of nevus recurrence were made on clinical rather than histologic grounds, and follow-up times were limited in some cases.

CONCLUSION

In this cohort, rates of clinical recurrence after biopsy of DN and benign nevi were extremely low. Re-excision of nevi, including mildly to moderately DN with a positive margin, may not be necessary.

The role of observation in the management of atypical nevi

OBJECTIVE

The definition and management of the atypical nevus remains a controversial issue. Some believe that atypical nevi are common variants of benign melanocytic nevi while others believe they are lesions intermediate between benign melanocytic nevi and melanoma. Therefore, the question of whether or not partially removed atypical nevi should be re-excised with clear margins in order to prevent their evolution into melanoma remains unanswered. Although studies have shown that most atypical nevi will never progress into melanoma, re-excision, when biopsy margins are positive, is commonly practiced. We argue that re-excision in such cases is not necessary.

METHODS

Our cohort study includes 55 previously biopsied atypical nevi that were not re-excised and which were followed for at least 5 years with a mean follow up time of 6.12 years.

RESULTS

The experimental group included 26 atypical nevi whose biopsy revealed at least one involved margin. The control group included 29 atypical nevi whose biopsy revealed clear margins. No melanomas were observed to arise in association with a pre-existing atypical nevus in either the experimental or control group during the follow-up period.

CONCLUSIONS

The results of our study support observation as a safe alternative to re-excision for incompletely removed atypical nevi. A large prospective study with longer follow up would be necessary to better answer the question of how often atypical nevi evolve into melanoma and over what time period this occurs.

Development of in situ melanoma after allogeneic bone marrow transplantation in Griscelli syndrome type II

GS is an uncommon autosomal recessive disorder characterized by pigmentary dilution of the skin and hair and in most patients by abnormal regulation of the immune system. Childhood melanoma is rare in the pediatric population. The best prognosis is achieved with early diagnosis and definitive surgical excision of melanoma. We report a case of a patient with GS type II and melanoma who was successfully treated by allogeneic bone marrow transplantation and surgical excision of the melanoma.

Mitoses in conventional melanocytic nevi

Given that nevi may grow in size, mitotic figures may be expected in melanocytic nevi. We reviewed the literature for studies addressing this issue. We sought to determine the number of mitotic figures we might discover upon review of a group of randomly collected, conventional nevi. We reviewed 157 nevi from patients and found seven nevi exhibiting mitotic figures, comprising 4% of our sample. We noted the location of the mitoses within the nevi, the presence of any congenital features, as well as other features such as signs of inflammation or irritation. Through this study we have shown that occasional mitoses occur within unremarkable, conventional nevi.

Melanozytäre Nävi in speziellen anatomischen Lokalisationen

Melanocytic nevi at special anatomical sites can evoke a histological picture easily leading to the false diagnosis of a highly atypical, dysplastic nevus or even malignant melanoma. It is therefore most important to recognize these lesions in order to differentiate them from "true" dysplastic nevi or malignant melanomas. The anatomical regions recognized as "special sites" are the head and neck, especially the ear, the milk line (axilla, mamae, mamillae, umbilicus, groin), acral regions (palms and soles, knee, dorsum of the foot) and flexural sites. The specific histological picture of these nevi is described as well as differential diagnostic considerations to differentiate these lesions from malignant melanomas.

A Subgroup of Melanocytic Nevi on the Distal Lower Extremity (Ankle) Shares Features of Acral Nevi, Dysplastic Nevi, and Melanoma In Situ

Melanocytic lesions in certain locations (eg, genital, breast, acral) may have histologic and clinical features simulating melanoma. Here we describe a group of lesions from the lower distal extremity and analyze their histologic features and possible relation to dysplastic nevi (DN) and melanomas. One hundred fifteen melanocytic lesions from the ankle were retrieved from January 1990 to August 2006 from the files of M. D. Anderson Cancer Center and were classified as benign melanocytic nevi (BN; n=17), DN (n=35), melanomas (MM; n=52), and melanocytic nevi of the ankle with atypical features (MNAAF; ie, cases that did not readily fit in any of the previous categories, n=11). Data analyzed included clinical (age and sex) and histologic features (circumscription, symmetry, cohesiveness of nests, suprabasal melanocytes, confluence, single-cell proliferation, nuclear chromasia, size, and nucleolar features). Follow-up was collected for all MNAAF. MNAAF differ from the other types of lesions in regard to sex incidence (73% in women). The median age of those patients MNAAF was 47 years (range 29 to 76 y). All MNAAF showed moderate-severe architectural disorder whereas 78% showed only mild-moderate cytologic atypia. No MNAAF cases had recurred after follow-up (4 mo to 13 y). This study highlights a group of melanocytic lesions located on the ankle that share histologic features with acral nevi, DN, and melanoma. These lesions are more predominant in females and have moderate to severe architectural atypia but only mild-moderate cytologic atypia. After complete excision, follow-up data indicate an apparently benign outcome. Pathologists should be aware of this type of lesions to avoid overdiagnosis of melanoma.

Method of biopsy and incidence of positive margins in primary melanoma

BACKGROUND

The staging of patients with primary melanoma is dependent on adequate sampling of the tumor thickness. Initial biopsies with a positive deep margin suggest inadequate sampling, potentially limiting accurate staging and affecting treatment decisions.

METHODS

To determine the efficacy of shave biopsy to adequately sample the tumor, we retrospectively reviewed our pathology database for original pathology reports of primary melanomas accessioned between 01/01/04 and 6/30/05. The biopsies were evaluated by technique, the presence of tumor at the margins of the specimen, and specimen thickness.

RESULTS

We identified 240 cases of primary melanoma; 223/240 were analyzable. The specimens were divided by biopsy technique (excisional, n = 51; punch, n = 44; and shave, n = 128). Shave and punch specimens had a significantly higher percentage of positive margins than excisional specimens (50, 68, and 16%, respectively; P < 0.0001). Shave specimens had a significantly higher percentage of positive deep margins than punch or excisional specimens (22, 7, and 2%, respectively; P = 0.0009). For melanomas <or=1 mm, shave specimens had a significantly higher percentage of positive deep margins than punch or excisional specimens (17, 0, and 0%, respectively; P = 0.0014). There was a significant difference in specimen thickness (P = 0.0005), with shave specimens being the thinnest.

CONCLUSIONS

The presence of tumor at the lateral margin of punch biopsies is an expected result, since this method is often used to diagnose lesions with a large diameter. The presence of positive deep margins in 22% of shave biopsy specimens compromises the ability of this technique to properly stage patients.