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BACKGROUND Imiquimod cream may be used as a non-surgical treatment for lentigo maligna or as adjuvant therapy following excision to decrease the risk of recurrence. OBJECTIVES To evaluate histologic and clinical factors associated with clinical clearance of lentigo maligna treated with imiquimod. METHODS We performed a retrospective review of all patients diagnosed with lentigo maligna and treated with imiquimod between 1997 and 2019 at our academic institution. RESULTS We observed clinical clearance in 93% (66/71) of participants who received adjuvant imiquimod following surgery and 79% (19/24) in the primary non-surgical treatment group over a median of 38 months of follow-up. In the adjuvant therapy group, positive surgical margins were associated with a decreased rate of clinical clearance when compared to cases with close (

Patients with cutaneous malignant melanoma (CMM) are at increased risk of non-melanoma skin cancers (NMSCs) and possibly precancerous lesions.To analyse the association between CMM and not only NMSCs but also precursor lesions, actinic keratosis (AK) and Bowen disease (BD).The Finnish Cancer Registry data was used to calculate the age-standardized incidence ratio during 2000-2013 for basal (BCC) and squamous (SCC) cell carcinoma in patients with CMM. All tissue material collected from 70,420 subjects during 2000-2013 and reposited in the Biobank of Eastern Finland was used to calculate the age-standardized prevalence of BCC, SCC, BD and AK in CMM patients.In both genders, the age-standardized incidence ratio of BCC and SCC was increased in CMM patients. The age-standardized prevalence of NMSCs and precursor lesions was higher in patients with CMM than in those without CMM, and was higher in CMM patients with immunosuppression (IS) than in those without IS. The association of M-Snomed subtypes, lentigo maligna (LM), melanoma in situ (MIS) and malignant melanoma (MM) with AK and/or BD was stronger than with BCC. LM revealed the highest association with the combination of AKBD-SCC. Male subjects showed a higher age-standardized prevalence of CMM, MM and BCC than females, but the opposite was observed for AK.Melanoma increases the risk of NMSCs, and IS may enhance this risk. Both malignant and in situ subtypes of melanoma associate with not only BCC and SCC, but also precancerous lesions.

Most international clinical guidelines recommend 5–10 mm clinical margins for excision of melanoma in situ (MIS). While the evidence supporting this is weak, these guidelines are generally consistent. However, as a result of the high incidence of subclinical extension of MIS, especially of the lentigo maligna (LM) subtype, wider margins will often be needed to achieve complete histologic clearance. In this review, we assessed all available contemporary evidence on clearance margins for MIS. No randomized trials were identified and the 31 non-randomized studies were largely retrospective reviews of single-surgeon or single-institution experiences using Mohs micrographic surgery (MMS) for LM or staged excision (SE) for treatment of MIS on the head/neck and/or LM specifically. The available data challenge the adequacy of current international guidelines as they consistently demonstrate the need for clinical margins > 5 mm and often > 10 mm. For LM, any MIS on the head/neck, and/or ≥ 3 cm in diameter, all may require wider clinical margins because of the higher likelihood of subclinical spread. Histologic clearance should be confirmed prior to undertaking complex reconstruction. However, it is not clear whether wider margins are necessary for all MIS subtypes. Indeed, it seems that this is unlikely to be the case. Until optimal surgical margins can be better defined in a randomized trial setting, ideally controlling for MIS subtype and including correlation with histologic excision margins, techniques such as preliminary border mapping of large, ill-defined lesions and, most importantly, sound clinical judgement will be needed when planning surgical clearance margins for the treatment of MIS.

Background Achieving negative margins for melanoma in situ, lentigo maligna type can be challenging, particularly on cosmetically sensitive areas. Objective To assess the utility of intraoperative frozen section margin assessment using a teledermatopathology system in the treatment of head and neck lentigo maligna. Methods and materials Over a 6 year period, 96 patients with lentigo maligna had surgical excisions. The margins were assessed intraoperatively with frozen sections prepared in the manner used in Mohs surgery. The surgeon guided the frozen section slides around the margin while a dermatopathologist assessed the margin remotely. Results In 2/96 (2.1%) cases, the safety margin was positive (frozen sections were false negative). In 1 further case (1%) there was a recurrence of the melanoma 13 months following the excision. Conclusion The described method is effective in treating melanoma in situ, lentigo maligna type with clearance rates similar to previous studies for Mohs surgery.

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

Background There are no well-defined clinical factors to predict the risk of occult invasion in melanoma of the lentigo maligna type (LM) before complete histopathologic analysis. Objective To evaluate whether clinical size was a predictor of invasion in LM and subclinical extension. Methods Consecutive cases of LM were recorded in a prospectively maintained database from 2006 to 2019. Patient and tumor data were recorded during initial evaluation. The LM clinical area was calculated in square millimeters (length × width). All patients were treated with staged excision. Results We included 600 patients. The mean age was 65.9 years (standard deviation, 12.3; range, 27-95 years); 62.8% (n = 377) were men. The mean LM clinical area was 128.32 mm2 for in situ lesions versus 200.14 mm for invasive lesions (P = .1). Based on quantile regression, the median margin required for complete removal increased with LM clinical area. Limitations The study was performed in a tertiary cancer center with possible referral bias and more complex cases. Conclusions LM can present with variable clinical size, which may correlate with subclinical extension; however, the presence of invasion is not well estimated by LM clinical area.

Background The incidence of xeroderma pigmentosum (XP) in Yemen seems to be quite high but there are no previous reports. Objective To study the clinicoepidemiologic aspect of XP in Yemen. Methods All 40 patients (24 male and 16 female patients from 32 families) treated and followed between 1997 and 2014 were subjected to detailed analysis with the help of a standardized protocol. The diagnosis was based on clinical features and histopathologic data, when needed. The diagnosis of tumors was confirmed by histopathologic examination in all cases. Results The median age of onset of initial manifestations was 9.5 months, and that of malignant lesions was 7 years. Parents of the patients were not affected, but history of consanguinity was recorded in 38. Initial lesions, such as dryness of the skin and freckles on the face, were noticed in all patients. In addition, erythema of the face with photosensitivity was observed in 21 patients. Premalignant and malignant skin lesions observed later were actinic keratosis in 15 patients, lentigo maligna in one, squamous cell carcinoma (SCC) in 10, and basosquamous carcinoma in one. Eyes were affected with SCC in seven and malignant melanoma (MM) in two patients. SCC of the lip developed in two patients and that of the tongue in one patient. Judicious use of acitretin in 12 patients showed good result. Conclusion XP in Yemen is characterized by a relatively high incidence, high percentage of consanguinity in parents of the patients, early onset of initial manifestations, malignant tumors, and severe ocular and oral lesions. Acitretin showed good result.

Background A recently introduced dermoscopic method for the diagnosis of early lentigo maligna (LM) is based on the absence of prevalent patterns of pigmented actinic keratosis and solar lentigo/flat seborrheic keratosis. We term this the inverse approach. Objective To determine whether training on the inverse approach increases the diagnostic accuracy of readers compared to classic pattern analysis. Methods We used clinical and dermoscopic images of histopathologically diagnosed LMs, pigmented actinic keratoses, and solar lentigo/flat seborrheic keratoses. Participants in a dermoscopy masterclass classified the lesions at baseline and after training on pattern analysis and the inverse approach. We compared their diagnostic performance among the 3 timepoints and to that of a trained convolutional neural network. Results The mean sensitivity for LM without training was 51.5%; after training on pattern analysis, it increased to 56.7%; and after learning the inverse approach, it increased to 83.6%. The mean proportions of correct answers at the 3 timepoints were 62.1%, 65.5, and 78.5%. The percentages of readers outperforming the convolutional neural network were 6.4%, 15.4%, and 53.9%, respectively. Limitations The experimental setting and the inclusion of histopathologically diagnosed lesions only. Conclusions The inverse approach, added to the classic pattern analysis, significantly improves the sensitivity of human readers for early LM diagnosis.

Oral pigmentations are a heterogeneous group and can be the result of physiological activity of oral mucosal melanocytes, secondary to exogenous causes, associated with systemic or local diseases, or due to proliferative activity of melanocytes. Their diagnosis is critical because these lesions can be markers of internal diseases or, in the case of melanocytic proliferative processes, they may represent a malignant neoplasm. In the past decade, the use of reflectance confocal microscopy, a noninvasive imaging tool, has aided the analysis of such lesions, but the establishment of firm criteria in their evaluation is still lacking. This study evaluated a series of 19 cases of pigmented oral lesions and correlated the reflectance confocal microscopy findings with histopathological classical criteria. We found 13 cases of melanotic macule, 1 of them associated with Peutz-Jeghers syndrome and 2 with Laugier-Hunzinker syndrome; 1 melanocytic nevus; 2 lentigo maligna; 2 pigmented actinic cheilitis; and 1 case of postinflammatory pigmentation secondary to a lupus erythematosus oral discoid lesion. The main difference between benign and malignant lesions was the presence of atypical proliferation in lentigo maligna. Langerhans cells with thick dendritic processes, which may be present in other benign and inflammatory pigmentations is one of the main reasons for diagnostic pitfalls.

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.

Aim: The evaluation of the trend in the occurrence of melanoma nodulare, melanoma superficiale, lentigo maligna and melanoma in situ in the period of 2002–2017 in East Bohemia region in the Czech Republic. We examine if the annual numbers of hours of sunshine could affect the number of patients with melanoma. Method: In the peridod of 2002–2017, altogether 2230 patients with new diagnosis of melanoma were examined. We studied 1) If there is some trend in the occurrence of lentigo maligna and melanoma in situ, melanoma superficiale, and melanoma nodulare and if there is a difference in the age of patients with this diagnosis (adjusted calculation of specific kind of melanomas and adjusted calculation of age). 2) If the annual numbers of hours of sunshine affect the trend in the occurrence of melanoma and if the annual numbers of hours of sunshine affect the body site of melanoma. Results and conclusion: Our study confirmed that the number of patients with lentigo maligna and melanoma in situ had increased in East Bohemia region in the period of 2002–2017. The number of melanomas of nodular and superficial type does not increase. The total number of melanomas in this period does not increase either. No difference of the age of patients with melanoma nodulare, superficiale, lentigo maligna and melanoma in situ was confirmed. We confirmed no relation of the annual numbers of hours of sunshine to the number of melanoma and to the body site of melanoma.

Skin cancer is a broad term used to describe a number of different malignant indications of the skin. Skin cancers mostly comprise of the keratinocyte cancers [Basal Cell Carcinoma (BCC) and cutaneous Squamous Cell Carcinoma (SCC)], and melanoma. Surgical excision of these malignancies has been the preferred treatment of patients for decades. However, the decision to perform surgery can be affected by various considerations, including co-morbidities of the patient, the anatomical site of the lesion and potential intolerance for repeated excisions. Topical treatment of skin cancer may therefore be more appropriate in certain instances. Topical treatment potentially allows for higher drug levels at the tumor site, and may result in less overall toxicity than systemic agents. This review will specifically address the current agents used in topical treatment of skin cancers, and introduce emerging treatments from the natural product field that may also find utility in these indications.

Lentigo maligna (LM) can be difficult to diagnose and recurrence is not uncommon. In vivo reflectance confocal microscopy (RCM) improves diagnostic accuracy of LM. LM can be difficult to discern from coexistent metal-induced cutaneous hyperpigmentation (MICH). We are the first to describe three cases of LM associated with gold, silver, and metal oxide (from tattoos) and the RCM findings, respectively. The images obtained via RCM were analyzed by two RCM experts, and histopathology reviewed by a dermatopathologist. MICH under RCM appeared as intensely hyperreflective dots (when found freely) or clusters of variable sizes (when engulfed by macrophages) limited to the dermis. Dermal dendritic cells and melanophages were also found in association but distinct from the confluence of dendritic cells at the dermoepidermal junction observed in LM. We showed longitudinal changes within the dermis in MICH, not previously reported, where these hyperreflective dots congregate into clusters. RCM was able to distinguish the features of LM from MICH, delineate treatment margins, and monitor for recurrence.

The surgical approach to lentigo maligna is a challenge to dermatologists, given its clinical and histopathological particularities. Staged excision with paraffin-embedded, permanent sections for histopathological evaluation of surgical margins is an effective treatment of lentigo maligna because it enables complete excision of the tumor, at the same time preserving maximum amount of healthy tissue. We report a case series of 6 patients diagnosed with lentigo maligna who underwent this procedure in our Institution and we describe the procedure we used. Complete excision of the tumors was achieved with one to three levels, with margins of excision ranging from 2 to 8 mm. There were no local recurrences at the median follow-up of 16 months, obtaining 100% cure rate with this technique. These are comparable with the margins and number of levels of excision described in previous case series reported in the literature. The technique described herein for the treatment of lentigo maligna provides excellent cure rates for this type of cutaneous malignancy notorious for its challenging management.

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Background CONCORD-3 highlighted wide disparities in population-based 5-year net survival for cutaneous melanoma during 2000–2014. Clinical evidence suggests marked international differences in the proportion of lethal acral and nodular subtypes of cutaneous melanoma. Objectives We aimed to assess whether the differences in morphology may explain global variation in survival. Methods Patients with melanoma were grouped into the following seven morphological categories: malignant melanoma, not otherwise specified (International Classification of Diseases for Oncology, third revision morphology code 8720), superficial spreading melanoma (8743), lentigo maligna melanoma (8742), nodular melanoma (8721), acral lentiginous melanoma (8744), desmoplastic melanoma (8745) and other morphologies (8722–8723, 8726–8727, 8730, 8740–8741, 8746, 8761, 8770–8774, 8780). We estimated net survival using the nonparametric Pohar Perme estimator, correcting for background mortality by single year of age, sex and calendar year in each country or region. All-ages survival estimates were standardized using the International Cancer Survival Standard weights. We fitted a flexible parametric model to estimate the effect of morphology on the hazard of death. Results Worldwide, the proportion of nodular melanoma ranged between 7% and 13%. Acral lentiginous melanoma accounted for less than 2% of all registrations but was more common in Asia (6%) and Central and South America (7%). Overall, 36% of tumours were classified as superficial spreading melanoma. During 2010–2014, age-standardized 5-year net survival for superficial spreading melanoma was 95% or higher in Oceania, North America and most European countries, but was only 71% in Taiwan. Survival for acral lentiginous melanoma ranged between 66% and 95%. Nodular melanoma had the poorest prognosis in all countries. The multivariable analysis of data from registries with complete information on stage and morphology found that sex, age and stage at diagnosis only partially explain the higher risk of death for nodular and acral lentiginous subtypes. Conclusions This study provides the broadest picture of distribution and population-based survival trends for the main morphological subtypes of cutaneous melanoma in 59 countries. The poorer prognosis for nodular and acral lentiginous melanomas, more frequent in Asia and Latin America, suggests the need for health policies aimed at specific populations to improve awareness, early diagnosis and access to treatment. What is already known about this topic? The histopathological features of cutaneous melanoma vary markedly worldwide. The proportion of melanomas with the more aggressive acral lentiginous or nodular histological subtypes is higher in populations with predominantly dark skin than in populations with predominantly fair skin. What does this study add? We aimed to assess the extent to which these differences in morphology may explain international variation in survival when all histological subtypes are combined. This study provides, for the first time, international comparisons of population-based survival at 5 years for the main histological subtypes of melanoma for over 1.5 million adults diagnosed during 2000–2014. This study highlights the less favourable distribution of histological subtypes in Asia and Central and South America, and the poorer prognosis for nodular and acral lentiginous melanomas. We found that later stage at diagnosis does not fully explain the higher excess risk of death for nodular and acral lentiginous melanoma compared with superficial spreading melanoma.

Mohs micrographic surgery (MMS) is a precise and effective method commonly used to treat high-risk basal cell carcinoma and squamous cell carcinoma on the head and neck. Although the majority of evidence for MMS relates to keratinocyte cancers, there is published evidence for other types of skin cancer. This review aims to discuss the evidence for using MMS to treat six different types of skin cancer [malignant melanoma, lentigo maligna, dermatofibrosarcoma protuberans, atypical fibroxanthoma (AFX), microcystic adnexal carcinoma and pleomorphic dermal sarcoma (PDS)] particularly in the context of survival rates and cancer recurrence. These cancers were chosen because there was sufficient literature for inclusion and because MMS is most useful when cancers are contiguous, rather than for cancers with marked metastatic potential such as angiosarcoma or Merkel cell carcinoma. We searched MEDLINE, PubMed and Embase using the keywords: 'melanoma', 'mohs micrographic surgery', 'lentigo maligna', 'dermatofibrosarcoma protuberans', 'atypical fibroxanthoma', 'microcystic adnexal carcinoma' and 'pleomorphic dermal sarcoma' along with their appropriate synonyms, to identify the relevant English-language articles from 2000 onwards, given that literature for MMS on nonkeratinocyte cancers is sparse prior to this year. AMSTAR (A MeaSurement Tool to Assess systematic Review) was used to assess the validity of systematic reviews. Further high-quality, multicentre randomized trials are necessary to establish the indications and efficacy of MMS for rarer cancers, particularly for AFX and PDS, for which only limited studies were identified.

Lentigo maligna is an in situ melanoma which usually affects sun-damaged skin on the head and neck. In patients with lentigo maligna, the clinically visible demarcation often correlates poorly with the histopathologically confirmed demarcation. Micrograhic surgery of lentigo maligna offers certainty of the presence of clear histological margins and is at the same time tissue sparing. Because of the clear margins after micrographic surgery, this technique leads to fewer recurrences than standard excision.

Background A regional skin cancer prevention program in Eastern Finland revealed a relatively high age-standardized mortality due to malignant melanoma during 2013–2017. An explanation for this is needed. Purpose To analyse the 543 melanoma samples in 524 subjects collected during 2000–2013 at Kuopio University Hospital and reposited in the Biobank of Eastern Finland. A focus was directed to factors related to metastasis. Methods The samples were analysed anonymously by examining the histopathological report, referral text and the list of diagnoses. A possible state of immunosuppression was evaluated. Results The mean age at the diagnosis of malignant melanoma (MM), lentigo maligna (LM) and melanoma in situ was relatively high, i.e., 66.2, 72.1 and 63.3, respectively. Especially the MM type increased markedly during 2000–2013. In further analyses of a representative cohort of 337 samples, the proportion of nodular melanoma and LM/LMM melanoma was relatively high, 35.6 and 22.0%, respectively, but that from superficial spreading melanoma relatively low (33.8%). Metastasis correlated with immunosuppression, male gender, Clark level, Breslow thickness, ulceration, mitosis count, invasion into vessels and/or perineural area, microsatellites, melanoma subtype, body site, recidivism, and the absence of dysplastic nevus cells. Conclusion The marked increase in aggressive melanomas with associated metastasis, and the relatively high age at diagnosis, can partially explain the mortality. Supplementary Information The online version contains supplementary material available at 10.1186/s12885-021-08879-1.

Lentigo maligna (LM) is a melanocytic neoplasm found on chronically sun-exposed areas of the body, particularly the head and neck. It commonly occurs in the elderly and has been referred to as a "senile freckle." It has also been termed "Hutchinson melanotic freckle," as it was first described by John Hutchinson in 1892. LM is defined as melanoma in situ and thus confined to the epidermis. LM lesions that invade the dermis are termed lentigo maligna melanoma, 1 of the 4 subtypes of malignant melanoma.

Lentigo maligna (LM) can develop into lentigo maligna melanoma (LMM) with risk of metastatic dissemination. LMM may be underestimated on the basis of the initial biopsy. The invasion may affect both the therapeutic options and the prognosis.To identify the clinical features associated with invasive forms of LM and factors associated with its recurrence.A retrospective, single-centre study of consecutive LM and LMM histologically confirmed and treated by surgery between 2009 and 2014.In total, 175 patients with LM/LMM were surgically treated in our establishment. In men, lesions were more likely to be in the "peripheral zone" (41.8%), while in women they were seen more often in the "central zone" (P=0.001). In multivariate analysis, only the peripheral zone was found to be associated with a risk of invasion (P=0.008). The rate of recurrence was 9% and lesions were more likely to be primary LMM (P=0.0006) excised with clear margins.The treatment of choice in LM with non-clear margins must be re-excision, especially for lesions situated in the peripheral zone. Close follow-up is recommended due to risk of recurrence, even in the case of clear margins.

Primary bladder melanomas are rare and aggressive neoplasms. We herein described a new case and performed a review of the literature.We present the case of a 81-year-old woman with a primary mucosal melanoma of the bladder after a history of acral melanoma (KRAS mutated) and lentigo maligna of the forehead. Using PubMed, we found that in literature 38 cases were described.In our patients, during a transurethral resection (TURBT), two bladder lesions were detected. The histologic exam revealed a malignant melanoma, Mib1/ki67: 10-12%, PDL11%. No BRAF, NRAS or KRAS mutations were detected. She subsequently underwent a transurethral revision of the trigone and a partial cystectomy of the dome with bilateral pelvic lymph node dissection. Microscopical findings showed a residual 5 mm non-muscle-invasive melanoma of the bladder, with negativity of the surgical margins and of the 17 pelvic lymph nodes. No adjuvant treatment was proposed. To date the patient is disease-free.Primary bladder melanoma carries a poor prognosis and poses a therapeutic challenge to clinicians who manage patients with this rare condition. In our experience the multidisciplinary approach for the diagnosis and management of this rare cancer is mandatory.

Topical imiquimod 5% cream has been investigated as off-label primary or adjuvant treatment for melanoma in situ, lentigo maligna type (LM). Herein, we present the largest known case series of lentigo maligna treated with topical imiquimod, with up to 17 years of follow-up, and include a recurrence-free survival analysis. In this case series, 103 lesions were retrospectively evaluated for treatment response and recurrence following a course of topical imiquimod with or without tazarotene gel 0.1% pretreatment between January 1, 2002 and March 31, 2019, and prospectively followed through November 15, 2019. Over median follow-up of 5.1 years (mean = 6.2 years, S = 5.2 years, range, 0.08ndash;17.1 years), including 29.1% LM withgt;10 years follow-up, we observed a response rate of 97.1% (100/103), with 8 local recurrences (8/100, 8.0%) developing at mean 2.9 years (SD: 2.7 years). Local recurrence was significantly associated with a history of failed excision (P= 0.001),lt;60 applications of imiquimod (P= 0.04) and partial clinical clearance (P= 0.0003). Recurrence-free survival analysis demonstrated significant risk-stratification for low and high-risk groups (P= 0.0001). Long term risk for recurrence showed significant differences among low- and high-risk cases, with low-risk cases demonstrating favorable long-term outcomes, comparable to conventional and staged surgery. Our observed low recurrence in a large case series with long-term follow-up suggests the efficacy of topical 5% imiquimod for LM and emphasizes the need for randomized control trials comparing imiquimod with, or as an adjunct to, surgical treatment. J Drugs Dermatol. 2021;20(3):346-348. doi:10.36849/JDD.5660.

Despite the rapid recent advances in molecular analysis of tumors, which allow large-scale and high-resolution genomics, the "gold standard" for melanoma diagnosis continues to be histopathology, in conjunction with clinical characteristics and sometimes with important support of immunohistochemistry. Observations, where postulated that cutaneous melanomas may arise through two distinct pathways, discoveries such as that BRAFV600E mutations were mostly common in melanomas on sun-exposed skin with little solar elastosis and seminal works for melanoma progression and evolution set the groundwork for the new WHO Classification of Melanoma: a classification of melanoma that not only encompasses histologic but also clinical, epidemiologic, and genetic characteristics. The melanomas were divided into those etiologically related to sun exposure and those that are not, based on their mutational signatures, anatomic site, and epidemiology. On the basis of degree of associated solar elastosis melanomas on the sun exposed skin were further divided by the histopathologic degree of cumulative solar damage (CSD) of the surrounding skin, into low and high CSD. On the low-CSD group of melanomas are included superficial spreading melanomas, while the high-CSD melanomas encompasses lentigo maligna and desmoplastic melanomas. The "non-CSD" classification includes acral melanomas, some melanomas in congenital nevi, melanomas in blue nevi, Spitz melanomas, mucosal melanomas, and uveal melanomas. Nodular and nevoid melanoma may occur in any pathway. A group of intermediate tumors termed melanocytoma is proposed for tumors that in addition to mutations that activate the MAPK pathway, harbor multiple driver mutations, and they are either low-grade or high-grade, to indicate that they may carry a higher risk of malignant transformation. In this review a summary of the most recent WHO classification of melanoma is provided. A short analysis of essential histopathologic prognostic parameters is also provided. The new classification of melanoma discriminates distinct types of melanoma based on their clinicopathologic, and genomic characteristics. Undoubtedly, melanoma research will continue to evolve as new clinical, pathological, molecular data accumulates. The challenge of the forthcoming years is to better characterize the intermediate category of melanocytic lesions.

Lentigo maligna/lentigo maligna melanoma (LM/LMM) affects chronically sun-damaged skin of the head and neck with a slow radial growth phase. It is characterised by predominantly lentiginous proliferation of small, but atypical melanocytes with occasional upward scatter in an atrophic epidermis. It is not uncommon for pathologists to receive partial or scouting biopsies to assess for LM. This makes the interpretation of symmetry and circumscription of the lesions challenging. Therefore, both cytologic and architectural criteria should be taken into consideration to render an accurate diagnosis of melanoma. Moreover, pathologists should be vigilant to avoid missing invasion, as this can change the treatment plan and prognosis. Herein, we aim to discuss important pitfalls in the diagnosis of LMM and its invasive component. Some of these caveats are differentiating between true invasion versus adnexal involvement by the in situ component or an incidental intradermal nevus, detection of microinvasion and multifocal invasion, and recognition of desmoplastic/spindle cell melanoma component.