The steadily growing problem of lentigo maligna and lentigo maligna melanoma in Australia: Population-based data on diagnosis and management

Lentigo maligna: a comprehensive review on diagnosis and treatment

Lentigo maligna (LM), a form of melanoma in situ, and LM melanoma (LMM), its invasive counterpart, exhibit distinctive epidemiology, risk factors, and clinical features compared to other melanoma subtypes. Notably, LM occurs on chronically sun-damaged skin presenting as a slow-growing, ill-defined patch which makes it difficult to diagnose and to treat. Additionally, while LM generally presents a favourable prognosis, it can also lead to dermal invasion and behave similarly to other melanomas with the same Breslow thickness. Hence, surgery continues to be the cornerstone treatment. Wide excisions are often necessary, but challenges arise when these lesions manifest in cosmetically sensitive regions, limiting the feasibility and desirability of large excisions. Specialized approaches, including margin-controlled surgery and image-guided treatment with reflectance confocal microscopy, have been developed to address these issues. Other non-surgical treatments such as cryosurgery, imiquimod, radiotherapy, or photodynamic therapy, may also be used but commonly present with recurrent/persistent disease. Herein we comprehensively review the existing literature on the management of LM/LMM, and discus the potential new advances on managing this challenging skin cancer.

Incidence trends of lentigo maligna and lentigo maligna melanoma in the United States from 2000 to 2019

BACKGROUND

Information on lentigo maligna (LM) and lentigo maligna melanoma (LMM) in the 21st century is scarce. We aimed to elucidate the incidence of LM and LMM using the Surveillance, Epidemiology, and End Results (SEER) 17 Registries.

METHODS

The data of patients diagnosed between 2000 and 2019 were extracted from the SEER database. The percentage of LM/LMM cases among all melanoma patients, age-standardized incidence rates, estimated annual percentage changes, and the cumulative incidence of LMM after LM were calculated.

RESULTS

The SEER data yielded 95,175 patients with LM/LMM between 2000 and 2019. Cases of LM/LMM accounted for 15.7% of all melanomas. The age-standardized incidence per 100,000 person-years for LM increased from 4.16 to 5.61 and for LMM from 1.33 to 2.35 between 2000 and 2019. The annual increase in incidence of LM was 2.42%, and that of LMM was 3.32%. The cumulative incidence of LMM after a primary LM after 10-year follow-up was 0.94%.

CONCLUSIONS

This study provides the first comprehensive analysis of the epidemiological status of LM/LMM in the United States in the 21st century using the population-based SEER data.

Lentigo maligna: a review

Lentigo maligna (LM) is a melanoma in situ with distinct clinical features and histology. It commonly affects men after the sixth decade of life. Incidence rates of LM have increased based on early 21st century data from different countries; however, data are suboptimal. Data from England show a plateauing crude incidence between 2013 and 2019. By comparison, invasive melanoma and other types of melanoma in situ commonly appears in younger age groups (median age 58 and 67 years old, respectively) and incidence is rising. The most important risk factors for LM include fair skin and cumulative ultraviolet solar radiation exposure. Although LM is limited to the epidermis and connected skin adnexa, it may progress to invasive LM melanoma. The reported rate of malignant progression varies, reflecting a challenge for LM epidemiology research as often lesions are removed on diagnosis. LM poses a challenge in diagnosis and management. Although it can be diagnosed clinically or dermoscopically, histopathological assessment of biopsied skin tissue remains the gold standard. Reflectance confocal microscopy allows for better appreciation of the complexity of LM at a cellular level, often progressing beyond clinical margins. Management of LM may involve Mohs micrographic surgery or excision, although recurrence may occur even with 5 mm clinical margins. Imiquimod cream may be effective, but incomplete treatment and recurrence has been reported. Conservative management with observation or radiotherapy may be used in selected patients' cases. Five-year net survival rates are excellent. This paper reviews the natural history, epidemiology, aetiology, pathogenesis, diagnosis and management of LM.

Lentigo maligna and lentigo maligna melanoma in young patients in Australian tertiary centres

This was a retrospective study of all patients with a diagnosis of lentigo maligna or lentigo maligna melanoma at 50 years of age or younger at the time of their first diagnosis in two Australian tertiary centres. The low recurrence rate in younger patients in this study warrants further investigation. Early diagnosis in young patients is crucial to allow early treatment and lifestyle changes to reduce actinic damage and subsequent development of further melanomas.

In vivo reflectance confocal microscopy can detect the invasive component of lentigo maligna melanoma: Prospective analysis and case-control study

BACKGROUND

Lentigo maligna (LM), a form of melanoma in situ, has no risk of causing metastasis unless dermal invasive melanoma (LMM) supervenes. Furthermore, the detection of invasion impacts prognosis and management.

OBJECTIVE

To assess the accuracy of RCM for the detection of invasion component on LM/LMM lesions.

METHODS

In the initial case-control study, the performance of one expert in detecting LMM at the time of initial RCM assessment of LM/LMM lesions was recorded prospectively (n = 229). The cases were assessed on RCM-histopathology correlation sessions and a panel with nine RCM features was proposed to identify LMM, which was subsequently tested in a subset of initial cohort (n = 93) in the matched case-control study by two blinded observers. Univariable and multivariable logistic regression models were performed to evaluate RCM features predictive of LMM. Reproducibility of assessment of the nine RCM features was also evaluated.

RESULTS

A total of 229 LM/LMM cases evaluated by histopathology were assessed blindly and prospectively by an expert confocalist. On histopathology, 210 were LM and 19 were LMM cases. Correct identification of an invasive component was achieved for 17 of 19 LMM cases (89%) and the absence of a dermal component was correctly diagnosed in 190 of 210 LM cases (90%). In the matched case-control (LMM n = 35, LM n = 58), epidermal and junctional disarray, large size of melanocytes and nests of melanocytes were independent predictors of LMM on multivariate analysis. The interobserver analysis demonstrated that these three features had a fair reproducibility between the two investigators (K = 0.4). The multivariable model including those three features showed a high predictive performance AUC = 74% (CI 95% 64-85%), with sensitivity of 63% (95% CI 52-78%) and specificity of 79% (CI 95% 74-88%), and likelihood ratio of 18 (p-value 0.0026).

CONCLUSION

Three RCM features were predictive for identifying invasive melanoma in the background of LM.

Spaghetti Technique Versus Wide Local Excision for Lentigo Maligna Affecting the Head and Neck Regions: Surgical Outcome and Descriptive Analysis of 79 Cases from a Single Practice Cohort

INTRODUCTION

Lentigo maligna is a subtype of melanoma in situ that typically affects the head and neck region with an increasing incidence. Margin-controlled techniques, such as spaghetti technique (ST), have gained popularity over wide local excision (WLE) with a margin of 5 mm.

OBJECTIVES

To evaluate the outcomes of lentigo maligna cases in the head and neck area treated by either WLE or ST in a tertiary referral hospital. The secondary goal was to describe the demographic and clinical characteristics of our series.

METHODS

Cohort study of patients diagnosed with lentigo maligna on the head and neck region between January 2014 and February 2022 in a tertiary hospital.

RESULTS

In total, 79 lentigo maligna were studied, corresponding to 77 patients. Fifty-three lesions (67%) were treated with WLE and 26 (33%) with ST. The mean age of the patients was 73 years and 58% were men. Most of the tumors were located on the cheek (50%) and mean lesion diameter was 2.2 cm for the ST group and 1.2 cm for the WLE group. Mean duration follow-up was 44 months. There were two local recurrences in the WLE group (2/53; 3.7%) and none in the ST group.

CONCLUSIONS

Both WLE and ST are appropriate surgical approaches for lentigo maligna. ST offers an efficient alternative to Mohs surgery for treating lentigo maligna in the head and neck area, especially when guided by reflectance confocal microscopy.

Clinical findings are not helpful in detecting lentigo maligna melanoma in patients with biopsy-proven lentigo maligna

BACKGROUND

Lentigo maligna (LM) based on biopsy material might be lentigo maligna melanoma (LMM) after excision.

OBJECTIVES

Investigate whether clinical and dermoscopic mapping increases the detection rate of LMM when investigating staged excision specimens of biopsy proven LM.

METHODS

Patients with biopsy-proven LM planned for staged excision were included. Using clinical inspection and dermoscopy, spots suspicious for LMM were marked. After the excision, needles were placed at the marked spots. Histological examination using vertical sections was done at the needles followed by the standard amount of vertical sections.

RESULTS

In 28 of the 58 biopsy-proven LM, there was clinical suspicion of LMM, only 3 of these 28 cases were upgraded into LMM. These three cases showed LMM in other sections, whereas only 1 case showed LMM around the needle. Within the group without clinical suspicion of LMM, 2 cases were LMM. Biopsy-proven LM were in fact LMM in 8.6% of the cases and were found without the clinical guidance of the dermatologist.

CONCLUSIONS

8.6% of the biopsy-proven LM were LMM after complete histological examination. In this study, the dermatologist was not able to increase the detection rate of LMM by using clinical and dermoscopic mapping.

Complex melanoma of the scalp: Diagnosis and management aided by confocal microscopy

Melanomas of lentigo maligna subtype are a steadily growing problem and frequently represent a clinical challenge. A case is reported of a complex melanoma of the scalp illustrating the critical role of confocal microscopy for optimal diagnosis and management.

A practical guide on the use of imiquimod cream to treat lentigo maligna

Lentigo maligna (LM) is a common in situ melanoma subtype arising on chronically sun-damaged skin and mostly affects the head and neck region. Localisation in cosmetically sensitive areas, difficulty to obtain wide resection margins and advanced patient age/comorbidities have encouraged investigation of less invasive therapeutic strategies than surgery in managing complex cases of LM. Radiotherapy and imiquimod have emerged as alternative treatment options in this context. The treatment of LM with imiquimod cream can be challenging due to the nature of the disease including its often large size, variegated appearance, involvement of adnexal structures, poorly defined peripheral edge and frequent localisation close to sensitive structures such as the eyes and lips, and elderly patients with multiple comorbidities. Prolonged and unpredictable inflammatory reaction and side effects and compliance with a patient-delivered therapy can also be challenging. In the literature to date, studies evaluating the use of imiquimod to treat LM have utilised varying methodologies and provided short follow-up and these limitations have impaired the development of clear guidelines for dosage and management of side effects. Based on our multidisciplinary experience and review of the literature, we propose practical clinical strategies for the use of imiquimod for treating LM, detailing optimal administration procedures in various clinical scenarios and long-term management, with the aim of facilitating optimal patient outcomes.

Risk factors for melanoma by anatomical site: an evaluation of aetiological heterogeneity

BACKGROUND

Melanoma aetiology has been proposed to have two pathways, which are determined by naevi and type of sun exposure and related to the anatomical site where melanoma develops.

OBJECTIVES

We examined associations with melanoma by anatomical site for a comprehensive set of risk factors including pigmentary and naevus phenotypes, ultraviolet radiation exposure and polygenic risk.

METHODS

We analysed harmonized data from 2617 people with incident first invasive melanoma and 975 healthy controls recruited through two population-based case-control studies in Australia and the UK. Questionnaire data were collected by interview using a single protocol, and pathway-specific polygenic risk scores were derived from DNA samples. We estimated adjusted odds ratios using unconditional logistic regression that compared melanoma cases at each anatomical site with all controls.

RESULTS

When cases were compared with control participants, there were stronger associations for many naevi vs. no naevi for melanomas on the trunk, and upper and lower limbs than on the head and neck (P-heterogeneity < 0·001). Very fair skin (vs. olive/brown skin) was more weakly related to melanoma on the trunk than to melanomas at other sites (P-heterogeneity = 0·04). There was no significant difference by anatomical site for polygenic risk. Increased weekday sun exposure was positively associated with melanoma on the head and neck but not on other sites.

CONCLUSIONS

We found evidence of aetiological heterogeneity for melanoma, supporting the dual pathway hypothesis. These findings enhance understanding of risk factors for melanoma and can guide prevention and skin examination education and practices.

Lentiginous melanoma (lentigo maligna and lentigo maligna melanoma) in Australia: clinicopathological characteristics, management and recurrence rates after 10-year follow-up at a tertiary centre

BACKGROUND

Lentiginous melanoma or lentigo maligna is a slow-growing type of melanoma frequently arising in sun-damaged skin and often first diagnosed in the elderly. Few studies report long-term follow-up.

OBJECTIVES

To define characteristics of lentiginous melanoma in situ (LM) and invasive lentiginous melanoma (LMM) in Australian patients managed at a tertiary centre and describe local recurrence or treatment failure rates after long-term follow-up.

METHODS

Retrospective single-centre study of LM/LMM patients evaluated between January 2005 and March 2007. Medical and photographic records were reviewed.

RESULTS

One hundred two patients were included, with a total of 117 lesions (70 LM and 47 LMM). Seventy-nine were new primary LM/LMM, and 38 were recurrences. Primary cases were mostly pigmented (71%), while 77% of recurrent cases were partially pigmented/light brown or amelanotic. The margins were clinically ill-defined in the majority of cases (64% of primary cases and 94% of recurrent cases). Dermoscopy of the primary LM/LMM showed either classic 'common' melanoma features (33%) or classic LM/LMM features (41%), while 95% of recurrent cases had no features for melanoma or LM/LMM. Primary cases that were initially excised (113, 97%) had mean histopathological clear margins of 4.9 mm (range 0.1-22 mm). The median follow-up time was 7.5 years (95% CI 5.2-10.0) with more than 10-year follow-up in 32% and 5-10 years in 24% of patients. There were 44 (38%) recurrences over the entire follow-up period. Half of the patients who recurred did so within the first 3.8 years after the first treatment.

CONCLUSION

LM/LMM often recur late and are clinically subtle; therefore, careful monitoring and long-term follow-up are required.

Lentigo Maligna: Clinical Presentation and Appropriate Management

Lentigo maligna (LM) is a type of melanoma in situ that has distinctive characteristics regarding epidemiology, risk factors and clinical features. In addition, LM has a potential to progress to an invasive tumor with potentially aggressive behavior: lentigo maligna melanoma (LMM). Overall, LM has a very good prognosis, whereas LMM has the same prognosis as other invasive melanomas with similar Breslow thickness. LM/LMM represents a challenging entity not only regarding the diagnosis but also regarding the management. Diagnostic criteria are not well established, and there is an overlap of clinical, dermoscopic and pathological features with other benign pigmented skin lesions such as lentigines, pigmented actinic keratoses or macular seborrheic keratoses. LM/LMM's common appearance within photodamaged skin makes lesion border identification difficult. Wide excisions are often required, but since LM/LMM typically appears on cosmetically sensitive areas such as the face, sometimes large excisions are not possible nor desirable. In this sense, specialized approaches have been developed such as margin-controlled surgery or image-guided treatment using reflectance confocal microscopy. Other treatments for LM such as cryosurgery, imiquimod, radiotherapy or photodynamic therapy have been proposed, although recurrence/persistence is common. The current manuscript reviews extensively the published data regarding the diagnosis, treatment and management of both complex entities LM and LMM.

Melanomas of the scalp: is hair coverage preventing early diagnosis?

BACKGROUND

Scalp melanomas are usually thicker and show worse prognosis than other sites and other head and neck melanomas. One hypothesis to explain this aggressive behavior could be diagnosis delay attributed to hair concealment of lesions.

METHODS

Primary melanomas of the scalp diagnosed over two decades at four reference centers in Australia and Italy were included. Hair coverage and visibility of the lesions were assessed on preoperative photographic documentation by two investigators and correlated with some prognostic factors (Breslow thickness, mitotic rate, and ulceration). Patients records and pathology reports provided clinical and histological data.

RESULTS

The majority of 113 melanomas included were located on easily visible areas of the scalp - hairless scalp (49%) or hairline (15%). The remaining ones (36%), considered to be hair-covered, showed more frequently thinning of hair (63%) than a dense hair coverage (37%). Melanomas of "hairy scalps" were more frequently invasive (81%) and had higher median Breslow (0.8 ± 1.3 mm) than those arising on bald scalps or areas with thinning of hair (43%; 0 ± 0.6 mm), P = 0.004. However, when considering only the invasive cases (n = 55), Breslow thickness and mitotic rate were not statistically different between concealed and easily visible areas. Melanomas detected by a doctor were thinner than those first noticed by the patient, relatives, or a hairdresser (P < 0.001).

CONCLUSIONS

Most scalp melanomas arose on easily visible areas, which are more prone to ultraviolet damage. Hair-covered ones, despite rare, could be overlooked during examination. Proactive screening of the scalp area should be encouraged.

Clinical outcomes following surgical treatment of lentigo maligna of the head and neck

INTRODUCTION

Lentigo maligna (LM), a subtype of melanoma in-situ commonly occurring in the head and neck region, often presents a treatment challenge due to anatomical constraints, particularly on the face of mostly elderly patients. This study sought to assess the clinical outcomes of wide local excision of head and neck LM, identify predictors of recurrence and define optimal excision margins.

MATERIALS AND METHODS

Patients with LM treated between January 1997 and December 2012 were identified from the large institutional database of a tertiary center and their data were analyzed.

RESULTS

In 379 patients, 382 lesions were eligible for analysis. Median maximal lesion diameter was 10.5 mm. The mean surgical excision and histopathological clearance margins were 6.2 mm and 4.0 mm, respectively. Median follow-up was 32 months. The LM recurrence rate was 9.9%, and subsequent invasive melanoma developed in 2.3% of cases (mean Breslow thickness 0.7 mm). The recurrence rate was 27.2% if the histological margin was <3.0 mm (median time to recurrence 46.5 months) compared with 2.6% if the margin was ≥3.0 mm. The mean surgical margin required to achieve a histological clearance of ≥3.0 mm was 6.5 mm.

CONCLUSIONS

Our data suggest that to minimize recurrence, a histological margin of ≥3.0 mm is required. To achieve this, a surgical margin of ≥6.5 mm was required. This is greater than the 5 mm margin recommended in some national guidelines. Careful long-term follow-up is required for all patients because of the risk of recurrence.

Is more dose and skin reaction required when treating early lentigo maligna definitively with radiotherapy? A case series

Introduction: Atypical intraepidermal melanocytic proliferation (AIMP) is an early form of lentigo maligna (LM) which itself is a precursor to melanoma. It presents commonly on the head and neck where tissue conserving therapies are attractive. When treating LM with imiquimod, dermatologists treat until a certain level of skin inflammation is achieved. Radiation oncologists treat to a set dose of radiation irrespective of the skin reaction at completion. The dose of radiotherapy for AIMP is unknown and these lesions are currently treated in the same manner as LM. Case series: Five immunocompetent patients (average age 80 years) with AIMP or early LM (ELM) on the head and neck region were treated with RADICAL radiotherapy (RT) protocols. All treatment sites were mapped with in vivo reflectance confocal microscopy (RCM) and measured on average 4.0 cm in diameter (range 2.0–6.0 cm). The median RT dose administered was 50 Gray (Gy) [45-54 Gy] in 1.8-2Gy per fraction to the planning target volume (PTV), usually by megavoltage electrons. All patients completed RT. The peak radiation acute skin toxicity observed at any time in all patients was only dry desquamation, equivalent to a grade 2 acute radiation dermatitis reaction by Common Terminology Criteria for Adverse Events (CTCAE) Version 5.0. At a median of follow up of 10 months, all patients had biopsy proven recurrence of AIMP (n=3) or LM (n=2). All recurrences were within the RT field. Patients were followed for an average total of five years post salvage treatment (range: 26 - 124 months). Discussion: This series raises questions. First, what radiation dose is required to cure AIMP and ELM? This series suggests that the same dose, if not higher, used in established in-situ disease, is required. Second, should radiation oncologists treat to a grade 3 skin reaction? It may be then advisable to use standard fractionation (2Gy or less) so that the peak RT reaction coincides with the end of treatment and allows for titration and extra dose to be added.

Outcomes of Staged Excision With Circumferential en Face Margin Control for Lentigo Maligna of the Head and Neck

BACKGROUND

Treatment practices vary for lentigo maligna (LM). Staged excision with circumferential margin control (SECMC) has the potential to achieve low recurrence rates.

OBJECTIVES

To evaluate the clinical outcomes of SECMC using permanent, paraffin-embedded sections and delayed reconstruction.

METHODS

We conducted a retrospective, uncontrolled, observational cohort study involving patients who underwent staged excision for LM of the head and neck at Women's College Hospital in Toronto, Canada, from September 2010 to March 2013. Recurrence and infection rates were ascertained from patient charts and postal surveys.

RESULTS

One hundred and two patients (45 female, 57 male) were included with a median follow-up time of 1410.5 (IQR 260-1756) days. The median age was 69 (IQR 61-79) years. Approximately one-fifth (21%, 21/102) of patients required greater than 0.5 cm margins to achieve histological clearance. One patient (1/102) upstaged to invasive melanoma based on the initial stage of excision. The infection rate was 6% (6/102) and the 5-year cumulative recurrence rate was 1.4% (95% CI 0.2-9.6%).

CONCLUSION

SECMC using permanent sections and delayed reconstruction appears to be a safe and effective treatment method for LM on the head and neck. Randomized trials are needed to help define the optimal treatment.