Melanocytes in nonlesional sun-exposed skin: A multicenter comparative study

doi:10.1016/j.jaad.2010.10.039

Journal of the American Academy of Dermatology

Volume 65, Issue 6, December 2011, Pages 1186-1193

https://doi.org/10.1016/j.jaad.2010.10.039 Get rights and content

Background

There are limited data regarding melanocyte density and distribution on sun-exposed skin of the head and neck, in particular, comparing morphology (hematoxylin-eosin [H&E] staining) and immunohistochemistry (Melan-A staining) on formalin-fixed tissue. Furthermore, comparisons of melanocyte density between distinct geographic populations have not been made using these methods. This information would be useful for physicians who use histologic criteria to diagnose and treat lentigo maligna.

Objective

We aimed to characterize the density and distribution of melanocytes using Melan-A and H&E stains on nonlesional sun-exposed skin of the face and neck, and compare the results between patients seen in Florida and Minnesota. We also aimed to quantify the presence and extent of features considered characteristic of melanoma in these noncancerous specimens of sun-damaged skin. The overall goal was to be able to provide this information to physicians who perform histopathologic interpretations of skin biopsy specimens to potentially prevent the overdiagnosis of melanoma.

Methods

In all, 100 patients undergoing Mohs micrographic and reconstructive surgery for basal cell and squamous cell carcinoma were enrolled, 50 each at the two sites. Permanent tissue sections were prepared from sun-exposed skin without clinical lesions. Melanocyte density and distribution were quantified.

Results

The overall median and 90th percentile, respectively, of melanocytes per high-power field was 9 and 14 on the H&E-stained sections and 11 and 19 on the Melan-A-stained sections. The means were 9.3 and 12.0, respectively (P < .001). There was evidence that melanocyte densities were higher in patients in Florida than in Minnesota, at least using H&E staining. There was evidence of lower melanocyte densities with increasing age, more so for Melan-A than H&E staining, and higher densities in men using Melan-A. Confluence was noted in 24% of cases using H&E and 45% using Melan-A. More than two thirds of these were classified as having mild confluence, whereas the others demonstrated higher amounts of confluence (3-8 melanocytes). Only 37 patients had a follicle present; of these, 7 patients had follicular extension although this did not extend beyond 1 mm in depth. Cytologic atypia was noted in 19 of the 100 patients; pagetoid spread was found in 3.

Limitations

This was a selected population of patients; results may not be generalizable to the wider population. Variables such as contours of the epidermis (rete density), density of hair follicles, and epidermal thickness may affect the reproducibility of the results. Melanomas were not included for comparison.

Conclusion

Relatively high melanocyte density, mild to moderate confluence of melanocytes, focal pagetosis, superficial follicular extension (<1.0 mm), and mild or moderate cytologic atypia may be observed in the absence of a melanocytic neoplasm. It is important for physicians to be aware of these findings so that such features are interpreted appropriately when making a histologic assessment that may ultimately influence therapy and outcome.

Section snippets

Data collection

Patients, from age 18 to 105 years, who were undergoing Mohs micrographic and reconstructive surgery for basal cell and squamous cell carcinoma of the face and neck were enrolled from Mayo Clinic, Jacksonville, FL (n = 50) and Mayo Clinic, Rochester, MN (n = 50). Patients with a history of radiation to the head and neck were excluded. The patients’ age, sex, type of tumor excised, personal history of dysplastic nevi or melanoma, and history of intense sun exposure in the 2 weeks before surgery

Results

A total of 100 study participants were recruited and enrolled, 50 each at Florida and Minnesota. Seventeen of the enrolled participants lived in a different state from the site at which they were recruited; these patients were included in the analysis. Table I shows a summary of the patient characteristics both overall and by site. There were no striking differences by site except that there were considerably more squamous cell carcinomas in Minnesota than in Florida.

Table II shows summaries of

Discussion

In the absence of quantitative guidelines for melanocyte density in sun-exposed skin, the histologic interpretation critical to appropriate diagnosis and therapy is often made subjectively. By better defining the normal degree of variability of melanocyte density and other features in practical and easily applicable terms, we aimed to delineate characteristics of nonlesional sun-exposed skin that would aid physicians facing this dilemma.

Similar to the previous study published by the principal

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Even when the microscopic findings are definitive in the center of the lesion, the proliferation of junctional melanocytes often gradually diminishes at the periphery, and blends with adjacent melanocytic hyperplasia (MH), making it difficult to define the boundary of the LM (Fig. 3). Although an increased density of junctional melanocytes can be observed in either LM or MH, nesting is not expected in MH, and pagetoid scatter is rare; therefore, when present, these features favor a diagnosis of LM.20,21 Routine sectioning (breadloafing) of tissue specimens results in histologic visualization of only a small percentage of the total peripheral margin; therefore, methods of more comprehensive assessment have been utilized for lentigo maligna specimens.
Premature cell senescence in human skin: Dual face in chronic acquired pigmentary disorders
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In older people, apart from a decreased number, melanocytes present a larger morphology, more dendritic and reduced tyrosinase activity (Yamaguchi et al., 2007; Tobin, 2011). Melanocyte dropout is less in sun-exposed areas, but these cells are functionally impaired and irregularly spaced, producing an irregular pigmentation on sun exposure (Hendi et al., 2006; and 2011). Thus, paradoxically, despite a decrease of active melanocytes, older skin has irregular pigmentation frequently associated with focal hyperpigmentation (solar lentigines) in sun-exposed areas of the skin (Gilchrest, 1979).
Although senescence was originally described as an in vitro acquired cellular characteristic, it was recently recognized that senescence is physiologically and pathologically involved in aging and age-related diseases in vivo. The definition of cellular senescence has expanded to include the growth arrest caused by various cellular stresses, including DNA damage, inadequate mitochondria function, activated oncogene or tumor suppressor genes and oxidative stress. While senescence in normal aging involves various tissues over time and contributes to a decline in tissue function even with healthy aging, disease-induced premature senescence may be restricted to one or a few organs triggering a prolonged and more intense rate of accumulation of senescent cells than in normal aging. Organ-specific high senescence rate could lead to chronic diseases, especially in post-mitotic rich tissue. Recently, two opposite acquired pathological conditions related to skin pigmentation were described to be associated with premature senescence: vitiligo and melasma. In both cases, it was demonstrated that pathological dysfunctions are not restricted to melanocytes, the cell type responsible for melanin production and transport to surrounding keratinocytes. Similar to physiological melanogenesis, dermal and epidermal cells contribute directly and indirectly to deregulate skin pigmentation as a result of complex intercellular communication. Thus, despite senescence usually being reported as a uniform phenotype sharing the expression of characteristic markers, skin senescence involving mainly the dermal compartment and its paracrine function could be associated with the disappearance of melanocytes in vitiligo lesions and with the exacerbated activity of melanocytes in the hyperpigmentation spots of melasma. This suggests that the difference may arise in melanocyte intrinsic differences and/or in highly defined microenvironment peculiarities poorly explored at the current state of the art. A similar dualistic phenotype has been attributed to intratumoral stromal cells as cancer-associated fibroblasts presenting a senescent-like phenotype which influence the behavior of neoplastic cells in either a tumor-promoting or tumor-inhibiting manner. Here, we present a framework dissecting senescent-related molecular alterations shared by vitiligo and melasma patients and we also discuss disease-specific differences representing new challenges for treatment.
Mohs micrographic surgery for melanoma: A prospective multicenter study
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The Mohs layer specimen was then processed using frozen sectioned tissue stained with hematoxylin and eosin and MART-1.12 Positive margins were defined as previously described13-15 and marked on the map. The involved margin was excised with an additional margin of not less than 2 mm and most typically 3 mm of normal-appearing skin.
Single-institution studies show that frozen section Mohs micrographic surgery (MMS) is an effective treatment modality for cutaneous melanoma, but no multi-institutional studies have been published.
To characterize the use of MMS in the treatment of melanoma at 3 academic and 8 private practices throughout the United States, to recommend excision margins when 100% histologic margin evaluation is not used, and to compare actual costs of tumor removal with MMS vs standard surgical excision.
Prospective, multicenter, cohort study of 562 melanomas treated with MMS with melanoma antigen recognized by T cells 1 immunostaining.
Primary trunk and extremity melanomas (noninvasive and invasive melanoma) achieved histologically negative margins in 97% of tumors with 10-mm margins, whereas 12-mm margins were necessary to achieve histologically negative margins in 97% of head and neck melanomas. Overall average cost per tumor treated was $1328.46.
Nonrandomized and noncontrolled study.
MMS with melanoma antigen recognized by T cells 1 immunostaining safely provides tissue conservation and same-day reconstruction of histologically verified tumor-free margins in a convenient, single-day procedure. When comprehensive margin evaluation is not used, initial surgical margins of at least 10 mm for primary trunk/extremity and 12 mm for head/neck melanomas should be used to achieve histologically negative margins 97% of the time.
Follicular involvement is frequent in lentigo maligna: Implications for treatment
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The diagnosis of LM and LMM relies on a multitude of histologic features, and it is important to recognize that follicular involvement alone does not confirm the diagnosis. The presence of superficial follicular involvement has been noted in normal-appearing, yet sun-damaged skin,17 as well as in other types of melanoma such as the rare variant follicular melanoma1,18,19 and folliculotropic metastases of melanoma.18 However, we advocate that the overall importance of follicular involvement within a confirmed diagnosis of LM not be underestimated, as it may ultimately affect treatment success.
Follicular involvement of lentigo maligna (LM) is considered a histopathologic hallmark, but its prevalence and characteristics have not been well defined. The depth of intrafollicular extension by neoplastic melanocytes may have clinical importance in the treatment of LM.
To describe the prevalence and features of follicular involvement in LM, including depth of follicular growth by melanocytes.
A single-center retrospective study of 100 consecutive cases of surgically excised LM that was treated from 2013 to 2015. The slide review for cases with residual LM on the debulk specimen was performed by a dermatologic surgeon and dermatopathologist to characterize follicular involvement.
Of 100 specimens, 72 met the inclusion criteria for histopathologic evaluation. Follicular involvement was seen in 95.8% of specimens (95% confidence interval, 88.3%-99.1%), with a mean of 68% of follicles involved in a single specimen. The mean depth of intrafollicular growth by lesional melanocytes was 0.45 mm (standard deviation, 0.23; range, 0.1-1.1 mm). Tumor cells were confined to the infundibular portion of the hair follicle in 60.9% of specimens.
Superficial follicular involvement is a ubiquitous finding in LM. When treatment options for LM with a depth-dependent modality aiming for tumor clearance are being considered, mean and maximum depths of involvement should be taken into consideration.
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Lentigo maligna melanoma (LMM) is a variant of melanoma that typically occurs on chronically sun-exposed skin of elderly individuals. Clinically, it presents as an irregular brown macule or patch on sun-damaged skin, most commonly on the head and neck region. Histologically, it is characterized by growth of predominantly solitary units of melanocytes with variable density initially along the dermoepidermal junction. This chapter discusses the clinical and histopathologic findings, ancillary tests, differential diagnosis, and management of LMM.
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Results of analyses for GET3,10,11,14-22,27,47-49,53,54 and SCT3,12,23,26,30,37,42,46,53 by anatomic location are in Supplemental Figs 1 and 2 (both available at http://www.jaad.org). Nine studies with 25 observations of MD by anatomic location were included (Fig 4).4,25,40,44,45,50-52,56 The overall estimate of MD was 955.05 cells/mm2 (95% CI, 880.89-1029.21).
Few studies have characterized reference values of normal human skin microanatomy parameters.
To quantify histologic measurements of epidermal thickness, melanocyte density, hair follicle density, and eccrine gland density as a function of age and anatomic site.
We searched the PubMed, Embase, Web of Science, and Cochrane databases for articles published through May 25, 2017. Two reviewers independently screened 2016 articles; 327 relevant articles and 151 additional articles found via forward or reference citations underwent full-text review by 1 of 4 reviewers for relevance, data extraction, and critical appraisal. Weighted averages, meta-analysis, and meta-regression were used in statistical analysis.
A total of 56 articles were included; when all anatomic locations were used, the overall estimates for epidermal thickness, melanocyte density, hair follicle density, and eccrine gland density were 99.75 μm (95% confidence interval [CI], 83.25-116.25), 955.05 cells/mm² (95% CI. 880.89-1029.21), 1.40 hairs/mm² (95% CI. 0.91-1.89), and 1.28 glands/mm² (95% CI. 0.91-1.64), respectively.
There was significant data heterogeneity across studies, possibly because of differences in histological techniques and absence of standardized microanatomy definitions.
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: The first two authors contributed equally to this work.

: Supported by Mayo Clinic, Jacksonville, FL, and Rochester, MN.

: Conflicts of interest: None declared.

: Reprints not available from the authors.

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DermatopathologyMelanocytes in nonlesional sun-exposed skin: A multicenter comparative study

Background

Objective

Methods

Results

Limitations

Conclusion

Section snippets

Data collection

Results

Discussion

J Am Acad Dermatol

J Am Acad Dermatol

J Invest Dermatol

J Invest Dermatol

J Invest Dermatol

Mod Pathol

The density and distribution of melanocytes adjacent to melanoma and nonmelanoma skin cancers

Dermatol Surg

Melanoma in situ versus melanocytic hyperplasia in sun-damaged skin: assessment of the significance of histopathologic criteria for differential diagnosis

Am J Dermatopathol

Melanocytes in long-standing sun-exposed skin: quantitative analysis using the MART-1 immunostain

Arch Dermatol

Dermatopathology
Melanocytes in nonlesional sun-exposed skin: A multicenter comparative study