Melanocyte Density in the Diagnosis of Melanoma In Situ in Sun-Damaged Skin

ABSTRACT

Histologic differentiation between melanoma in situ in chronically sun-damaged skin (CSDS) [lentigo maligna (LM)] and CSDS without malignancy is difficult because signs of melanocyte activation and proliferation are found in both. A potentially reliable and quantifiable criterion is melanocyte density (MD). Here, we evaluated whether and to what extent MD allows the distinction between LM and CSDS, which is particularly relevant for the evaluation of borderline cases and surgical margins.Articles assessing MD in LM and/or CSDS were evaluated in a systematic review. The results were categorized and compared according to staining. Cutoff values were included whenever stated.Twenty articles matched the selection criteria. Six hundred forty-four samples of CSDS and 227 samples of LM were considered. In each individual study, mean MD scores were higher for LM than for CSDS. However, looking at the overall study situation, it becomes clear that the data are very heterogeneous and show overlaps. Therefore, no reliable orientation value can be derived. Only 1 article defined a cutoff value.The data of MD in LM in contrast to CSDS were sparse, and a defined cutoff value was only mentioned in 1 article for microphthalmia-associated transcription factor, which cannot yet be generalized. Especially regarding the importance for the definition of surgical resection margins, this unsatisfactory data set highlights the need for further studies. More precise diagnostic criteria could spare some patients extensive and possibly disfiguring surgery.

Nevus Spilus With Dermatoheliosis: A Histologic Mimicker of Melanoma in Situ at Melanoma Excision Margins

ABSTRACT

Nevus spilus, or speckled lentiginous nevus, is a relatively common lesion that presents at birth or in early childhood. It consists of a background tan patch, which appears similar to a café au lait macule or lentigo simplex on histology, studded with various types of nevi. Rarely, these nevi can undergo malignant transformation to melanoma. When melanoma develops within a heavily photodamaged nevus spilus, evaluating excision margins may be challenging because the combined histologic features of nevus spilus and severe dermatoheliosis can mimic melanoma in situ. We report a case of an elderly man with extensive sun damage who developed malignant melanoma within an occult nevus spilus, resulting in multiple excisions with false-positive margins.

Staged Excision of Lentigo Maligna of the Head and Neck: Assessing Surgical Excision Margins With Melan A, SOX10, and PRAME Immunohistochemistry

BACKGROUND

Staged excision has emerged as a superior treatment option for lentigo maligna (LM) of the head and neck when compared with conventional wide local excision. Assessing surgical excision margins for remaining LM poses a diagnostic challenge.

OBJECTIVES

To determine whether immunohistochemical (IHC) staining with SOX10 and preferentially expressed antigen in melanoma (PRAME) aids in diagnosing LM on excision margins compared with conventional hematoxylin and eosin and Melan A IHC staining.

METHODS

This study included cases of LM of the head and neck treated with staged excision. Histological findings were reviewed according to standard criteria for the diagnosis of LM and compared with the results after IHC staining for Melan A, SOX10, and PRAME.

RESULTS

The cohort consisted of 35 sections. Based on hematoxylin and eosin and Melan A IHC staining, 23 sections were diagnosed as LM by the initial pathologist. Further staining with SOX10 IHC showed only 8 to be consistent with a diagnosis of LM and 9 revealing features of actinic melanocyte hyperplasia. PRAME was positive in 5 of the 8 cases of LM and negative in all 9 cases of actinic melanocyte hyperplasia (P = 0.009). The presence of melanocyte nests (P = 0.29) and pagetoid spread (P = 0.003) was the most reliable histological findings distinguishing LM from its mimics.

CONCLUSION

SOX10 is a more specific and sensitive marker for melanocytes when assessing for LM on excision margins compared with Melan A. The addition of PRAME can be useful to confirm or exclude the diagnosis in challenging cases.

Pigmented Macules on the Head and Neck: A Systematic Review of Dermoscopy Features

INTRODUCTION

Differentiating early melanoma from other flat pigmented lesions on the head and neck is challenging both clinically and dermoscopically, partly due to the wide differential diagnosis and the lack of specific diagnostic algorithms.

OBJECTIVES

To review publications covering the dermoscopic features of pigmented macules on the head and neck.

METHODS

Embase and PubMed (Medline) database from January 2015 to January 2021 were searched using a four-step search. Keywords used were dermoscopy/dermatoscopy or epiluminescence microscopy, lentigo maligna, lentigo maligna melanoma, lichen-planus-like-keratosis, solar lentigo, seborrheic keratosis, pigmented actinic keratosis (PAK), pigmented Bowen disease (pBD), pigmented intraepidermal carcinoma (pIEC) and head and neck.

RESULTS

The commonest reported dermoscopic features of facial melanoma were irregular dots, atypical dots/globules, asymmetric pigmented follicular openings, rhomboid gray/black structures, increased vascular network, brown globules/dots and a pattern of circles. Pseudopods, radial streaming, blue white veil, irregular blotches, scar-like depigmentation and atypical pigment network were recorded in low frequencies. For PAK, pBD and pIEC perifollicular erythema, white/yellow surface scale, linear wavy vessels around hair follicles, hair follicular openings surrounded by a white halo, evident follicles or follicular or keratotic plugs, rosette sign and sharply demarcated borders were the salient features.

CONCLUSIONS

Further studies are needed to determine the dermoscopic criteria for pigmented melanocytic and non-melanocytic lesions on the head and neck. Furthermore, there is a gap in the knowledge of site-specific dermoscopic features on specific sites, namely ears, nose, cheeks, scalp and neck which will also benefit from further studies.

Digital Quantification of Melanocytic Density in Resection Margins of Lentigo Maligna Using SOX10 Versus Hematoxylin-Eosin Staining

ABSTRACT

Lentigo maligna (LM) represents an overgrowth of atypical melanocytes at the dermal-epidermal junction of chronically sun-damaged skin. The presence of LM on sun-damaged skin poses a diagnostic challenge because the solar-induced melanocytic hyperplasia makes it difficult to assess the LM margins. Melanocytic density can be used to discriminate sun-damaged skin from LM. The aim of this study was to quantify the melanocytic density at the surgical margins of scanned whole-slide images of LM comparing sections stained with H&E and SOX10. Twenty-six surgically excised LM diagnosed at the Department of Pathology at Sahlgrenska University Hospital were collected. The slides that contained the closest surgical margin or harbored the highest density of melanocytes at the margin were selected for serial sectioning using H&E and SOX10. Whole-slide imaging at ×40 magnification was used, and a circular field with a diameter of 0.5 mm at the surgical margin was superimposed on the image. Five blinded pathologists reviewed the slides in a randomized order. In the majority of the cases (24/26), the pathologists identified more melanocytes on the SOX10 slides than those on the H&E slides. On average, 2.5 times more melanocytes were counted using SOX10 compared with H&E (P < 0.05). Furthermore, the average group SD on the H&E slides was 4.12 compared with 2.83 on the SOX10 slides (P = 0.004). Thus, the use of SOX10 staining leads to higher melanocytic density counts compared with H&E staining when assessing the surgical margins of LM. The use of SOX10 staining also significantly decreased the interobserver variability between pathologists.

A comparison of imaging software and conventional cell counting in determining melanocyte density in photodamaged control sample and melanoma in situ biopsies

BACKGROUND

Objective methods for distinguishing melanoma in situ (MIS) from photodamaged skin (PS) are needed to guide treatment in patients with melanocytic proliferations. Melanocyte density (MD) could serve as an objective histopathological criterion in difficult cases. Calculating MD via manual cell counts (MCC) with immunohistochemical (IHC)-stained slides has been previously published. However, the clinical application of this method is questionable, as quantification of MD via MCC on difficult cases is time consuming, especially in high volume practices.

METHODS

ImageJ is an image processing software that uses scanned slide images to determine cell count. In this study, we compared MCC to ImageJ calculated MD in microphthalmia transcription factor-IHC stained MIS biopsies and control PS acquired from the same patients.

RESULTS

We found a statistically significant difference in MD between PS and MIS as measured by both MCC and ImageJ software (P < 0.01). Additionally, no statistically significant difference was found when comparing MD measurements recorded by ImageJ vs those determined by the MCC method.

CONCLUSION

MD as determined by ImageJ strongly correlates with the MD calculated by MCC. We propose the use of ImageJ as a time-efficient, objective, and reproducible tool to assess MD.

Rate of Recurrence of Lentigo Maligna Treated With Off-Label Neoadjuvant Topical Imiquimod, 5%, Cream Prior to Conservatively Staged Excision

Importance

Staged excision of lentigo maligna (LM) often requires multiple stages and can result in significant cosmetic morbidity. Imiquimod cream has been used off-label as monotherapy in the treatment of LM and may be used in the neoadjuvant setting prior to staged excision as a strategy to reduce the size of the surgical margins required to confirm negative histologic margins.

Objective

To examine the rate of recurrence of LM in patients treated with neoadjuvant topical imiquimod, 5%, cream prior to conservatively staged excisions.

Design, Setting, and Participants

This was a retrospective medical record review of 334 patients with 345 biopsy-confirmed LM tumors from June 2004 to January 2012 who were treated with imiquimod prior to undergoing staged excisions at the University of Utah Medical Center and Huntsman Cancer Institute, large academic hospitals in Salt Lake City.

Interventions

Patients were treated with off-label imiquimod, 5%, cream 5 nights per week for 2 to 3 months. Those deemed to have an inadequate inflammatory response were also treated with tazarotene, 0.1%, gel twice weekly. Conservatively staged excisions, beginning with 2-mm margins, were then performed.

Main Outcomes and Measures

The rate of recurrence of LM after long-term follow-up.

Results

Patients included 235 men (70%) and 99 women (30%) with a mean (SD) age of 67 (13) years. Patients were treated with imiquimod cream for a mean of 2.5 months prior to undergoing conservatively staged excisions. There were 12 local recurrences (a rate of 3.9%) with a mean time to recurrence of 4.3 years and a mean length of follow-up of 5.5 years.

Conclusions and Relevance

Neoadjuvant topical imiquimod, 5%, cream prior to conservatively staged excisions for LM allowed for negative histologic margins with a median final margin of 2 mm and a rate of recurrence similar to reported recurrence rates with standard staged excisions by either Mohs surgery or en face permanent sections.

Strategies for Reducing Final Surgical Defect Sizes in the Treatment of Lentigo Maligna

BACKGROUND

Lentigo maligna (LM) is associated with disproportionately high surgical morbidity.

OBJECTIVE

The authors report on 2 strategies to reduce the surgical morbidity associated with LM.

METHODS

Forty LM lesions were removed with excisional biopsies without margins and closed with purse-string sutures. Invasive cases underwent staged excisions with 10-mm margins. Cases without invasion were treated with neoadjuvant topical imiquimod 5% cream (5 d/wk × 8 weeks) followed by conservative staged excisions with 2-mm margins using radial sections stained with hematoxylin and eosin and immunostaining with Mart-1, with or without SOX10.

RESULTS

Invasion was detected in 12/40 (30%) of the excisional biopsy specimens (average depth 0.45 mm). No invasion was detected in 28/40 (70%). All 24 patients who completed neoadjuvant topical imiquimod 5% cream before staged excisions had negative first-stage margins at 2 mm. Compared with average published margins for LM, this represents a 71.4% reduction in the required margin and an average reduction in the final surgical defect by 74%.

CONCLUSION

LM treatment by excisional biopsies with a purse-string closure enables accurate tumor staging and contracts the tumor footprint to its minimal size. Subsequent neoadjuvant imiquimod followed by a conservative staged excision with 2-mm margins allows for removal of LM with decreased surgical morbidity.

Is melanocyte density our last hope? Comparison of histologic features of photodamaged skin and melanoma in situ after staged surgical excision with concurrent scouting biopsies

Differentiating melanocytic hyperplasia (MH) on photodamaged skin from junctional lentiginous melanocytic proliferations (JLMP), early evolving melanoma in situ (MIS), or the periphery of a lesion of MIS on staged excision can be challenging. Although previous cross-sectional studies have elucidated important criteria for distinguishing MH on photodamaged skin from more concerning lesions, this study highlights a technique to treat JLMP and MIS with staged mapped excision and baseline scouting biopsies of adjacent nonlesional photodamaged skin to assist in determination of surgical margin clearance. Additionally, we compare the lesional and photodamaged control biopsies from the same patient to evaluate relevant histologic criteria that may be used to distinguish MH in photodamaged skin from JLMP/MIS, while minimizing confounding factors. There was a statistically significant difference (P ≤ 0.05) found for melanocyte density, irregular melanocyte distribution, melanocyte clustering, follicular infundibulum involvement, and nesting. However, criteria such as nesting, epithelioid cells and melanocyte clustering were seen in both photodamaged skin and MIS. These findings underscore the fact that histologic features of photodamaged skin can overlap with the histopathological features of MIS. Of all of the criteria evaluated, melanocytic density was the most objective histologic criterion and did not show overlap between the sun-damaged and JLMP/MIS groups.

A quantitative comparison between SOX10 and MART-1 immunostaining to detect melanocytic hyperplasia in chronically sun-damaged skin

Histologic differentiation of melanoma in situ (MIS) from solar keratosis on chronically sun-damaged skin is challenging. The first-line immunostain is usually MART-1/Melan-A, which can exaggerate the epidermal melanocytes, causing a diagnostic pitfall for MIS. By comparing MART-1 and SOX10 immunostaining, we scored the percentage of epidermal melanocytes per 2-mm diameter fields in pigmented actinic keratosis (n = 16), lichenoid keratosis (n = 7), junctional melanocytic nevus (n = 6), keratosis with atypical melanocytic proliferation (n = 17) and MIS (n = 10). These cases represented an older population (68 years median age) and the head and neck (50%) was the most common anatomic site. MART-1 score was significantly higher than SOX10 (P value <.05) in solar keratoses, but showed no difference in detecting melanocytic proliferations, demonstrating their equal detection rate of melanocytes. The sensitivity of both MART-1 and SOX10 was 100%, while their specificities were 17% and 96%, respectively. These results show that SOX10 is more specific than MART-1 in distinguishing epidermal melanocytes on sun-damaged skin by avoiding overdiagnosis of melanoma.

Risk Factors Predicting Positive Margins at Primary Wide Local Excision of Cutaneous Melanoma

BACKGROUND

A small percentage of patients will have positive histological margins after primary wide local excision (WLE) of cutaneous melanoma (CM). Risk factors that predict marginal involvement at WLE remain unclear.

OBJECTIVE

To identify risk factors associated with positive margins after WLE of CM.

MATERIALS AND METHODS

A retrospective review of patients treated at a single institution for CM with sentinel lymph node biopsy from 1997 to 2011 was conducted.

RESULTS

Positive margins occurred in 6% of patients. Patients with positive margins were older (72.4 vs 60.7, p < .001), had thicker tumors (3.6 vs 1.9 mm, p < .001), and often involved the head and neck region (p < .001). Patients with positive margins at WLE had positive margins on initial biopsy (p = .012) and a higher rate of a melanoma in situ component on initial biopsy (24% vs 11%, p = .02). The 5-year local recurrence rate was significantly different between those with positive and negative margins at WLE (16.0% vs 6.9%; p = .047).

CONCLUSION

Positive margins after WLE are uncommon. When a patient has multiple risk factors for positive margins at WLE, histologically clear margins should be obtained through mapped serial excision or Mohs micrographic surgery.

Reviewing Challenges in the Diagnosis and Treatment of Lentigo Maligna and Lentigo-Maligna Melanoma

Lentigo maligna (LM) and lentigo-maligna melanoma (LMM) are pigmented skin lesions that may exist on a continuous clinical and pathological spectrum of melanocytic skin cancer. LM is often described as a "benign" lesion and is accepted as a melanoma in situ; LM can undergo malignant transformation to particularly aggressive melanoma. LMM is an invasive melanoma that shares properties of LM, as well as exhibiting the metastatic potential of malignant melanoma. Unfortunately, LM/LMM diagnosis based on dermoscopy is rather ambiguous, and these lesions are often mistaken for junctional dysplastic nevi over sun-damaged skin, pigmented actinic keratosis, solar lentigo, or seborrheic keratosis. Diagnosis must be made on biopsy using distinct dermatopathologic features. These include a pagetoid appearance of melanocytes, melanocyte atypia, non-uniform pigmentation/distribution of melanocytes, and increased melanocyte density in a background of extensive photodamage. Advancements in immunohistochemical staining techniques, including soluble adenylyl cyclase (antibody R21), makes diagnosis easier and allows the definition of borders down to a single cell. After a pathologic diagnosis, there are a variety of treatment options, both surgical and non-surgical. Although surgical removal with a wide excision border is the preferred treatment due to decreased recurrence rates, experimental combination therapies are gaining popularity. However, no matter the treatment, LM/LMM carries a high recurrence rate, and patients must be monitored rigorously for recurrence as well as the appearance of additional skin lesions/cancers.

Soluble adenylyl cyclase antibody (R21) as a diagnostic adjunct in the evaluation of lentigo maligna margins during slow Mohs surgery

Margin-controlled staged excision (slow Mohs) has emerged as a preferred method for the treatment of lentigo maligna (LM). The interpretation of margins for LM is one of the most challenging tasks faced by a dermatopathologist. R21 is a mouse monoclonal antibody against soluble adenylyl cyclase (sAC), overexpressed in the nuclei of LM but not in native melanocytes. The objective of this study was to validate the use of sAC immunohistochemistry in histological assessment of slow Mohs surgery margins for LM. Seventeen randomly selected cases of patients who underwent slow Mohs surgery for LM at Lahey Clinic, Burlington, MA, were studied. Ninety-nine margins were stained with R21 and microphthalmia transcription factor antibodies and reevaluated blindly by 2 observers. Sixteen of 17 lesions expressed sAC. In all cases, observers agreed on interpretation of R21 stains. In 85 (86%) margins, there was concordance between routine sections and R21 stains. In 14 margins (14%), the results were discrepant. In 2 margins, R21 identified foci of LM missed on routine sections. In 8 margins, atypical melanocytes, interpreted as positive in routine sections, were negative for R21 questioning the accuracy of the original interpretation. Microphthalmia transcription factor stained nuclei of melanocytes in all margins. We found significant correlation between assessment of margins by sAC immunohistochemistry and routine histology. Evaluation of sAC expression using R21 antibody is a useful diagnostic adjunct in the evaluation of margins of LM during slow Mohs surgery.

Lentigo maligna and lentigo maligna melanoma: contemporary issues in diagnosis and management

Lentigo maligna and lentigo maligna melanomas present diagnostic and treatment dilemmas due to their frequent presence within a background of sun-damaged skin, and their location on cosmetically and functionally sensitive areas. As the incidence of this entity is increasing, diagnostic and management controversies have developed. While surgery remains the gold standard of treatment, nonsurgical treatment options are also emerging for both adjunctive and primary therapy.

Expression of soluble adenylyl cyclase in lentigo maligna: use of immunohistochemistry with anti-soluble adenylyl cyclase antibody (R21) in diagnosis of lentigo maligna and assessment of margins

CONTEXT

Soluble adenylyl cyclase (sAC) is an enzyme that generates cyclic adenosine monophosphate, a signaling molecule involved in regulating melanocyte functions. R21, a mouse monoclonal antibody against sAC, shows a striking pan-nuclear staining in lentigo maligna, indicating possible utility for diagnosis and margin assessment.

OBJECTIVE

To evaluate R21 in the diagnosis and evaluation of margins in lentigo maligna.

DESIGN

Thirty one re-excision specimens for lentigo maligna were evaluated for R21 expression using previously published protocol. In addition, 153 cases including 41 lentigo malignas, 30 non-lentigo maligna-type melanomas, 38 lentigos, and 44 nevi were evaluated using a modified stringent protocol to eliminate all nonmelanocyte staining.

RESULTS

The sensitivity of nuclear staining with R21 in lentigo maligna was 87.8%. Nuclear expression of sAC was observed in 40% of other melanomas and 2.3% of benign nevi. R21 did not stain nuclei of resting melanocytes but was observed in 28.9% of melanocytic hyperplasias. These cases were easily distinguished from lentigo maligna in routine sections. R21 staining facilitated extent of the lesion in resection margins. In cases examined under the less stringent conditions, interpretation was facilitated by comparing R21 and Mart1/Melan A staining. Greater than 9 pan-nuclear staining melanocytes within one high-power field along with a pan-nuclear sAC/Melan A ratio greater than 0.5 was consistent with a positive margin whereas 5 or less pan-nuclear staining melanocytes along with a sAC/Melan A ratio of less than 0.3 constituted a negative margin.

CONCLUSION

R21 is a useful diagnostic adjunct in the diagnosis and evaluation of margins in re-excision specimens in lentigo maligna.