The classification of malignant melanoma, its histological reporting and registration: a revision of the 1972 Sydney classification

Counting mitoses: SI(ze) matters!

Mitoses are often assessed by pathologists to assist the diagnosis of cancer, and to grade malignancy, informing prognosis. Historically, this has been done by expressing the number of mitoses per n high power fields (HPFs), ignoring the fact that microscope fields may differ substantially, even at the same high power (×400) magnification. Despite a requirement to define HPF size in scientific papers, many authors fail to address this issue adequately. The problem is compounded by the switch to digital pathology systems, where ×400 equivalent fields are rectangular and also vary in the area displayed. The potential for error is considerable, and at times this may affect patient care. This is easily solved by the use of standardized international (SI) units. We, therefore, recommend that features such as mitoses are always counted per mm2, with an indication of the area to be counted and the method used (usually "hotspot" or "average") to obtain the results.

Peripheral Palisading in Melanoma Mimicking Basal Cell Carcinoma: A Case Report

The incidence of melanoma has been increasing over the past few decades. Because of its phenotypic diversity, melanoma may present in various clinical and histopathological manifestations, and it can mimic varieties of skin lesions from benign to malignant and from epithelial to nonepithelial. Accurate diagnosis of melanoma is crucial because delayed treatment leads to worse prognoses. Here, we describe a case of melanoma in an 82-year-old man with an unusual histopathologic presentation, namely, the presence of neoplastic aggregates with a palisaded periphery resembling basal cell carcinoma.

Melanoma pathology: new approaches and classification

Cancer is caused by the accumulation of pathogenic alterations of the genome and epigenome that result in permanent changes that disrupt cellular homeostasis. The genes that become corrupted in this process vary among different tumour types, reflecting specific vulnerabilities and dependencies of the cell from which the cancer originated. This also applies to 'melanoma', a cancer that constitutes not one, but multiple diseases that can be separated based on their cell of origin, aetiology, clinical appearance and course, and response to treatment. In this article, we review the current classification of melanoma within distinct evolutionary pathways and the associated genetic alterations. In addition, we review the application of molecular diagnostics to the diagnosis of melanocytic tumours in the context of histopathological assessment.

The 2018 World Health Organization Classification of Cutaneous, Mucosal, and Uveal Melanoma: Detailed Analysis of 9 Distinct Subtypes Defined by Their Evolutionary Pathway

CONTEXT.—

There have been major advances in the understanding of melanoma since the last revision of the World Health Organization (WHO) classification in 2006.

OBJECTIVE.—

To discuss development of the 9 distinct types of melanoma and distinguishing them by their epidemiology, clinical and histologic morphology, and genomic characteristics. Each melanoma subtype is placed at the end of an evolutionary pathway that is rooted in its respective precursor, wherever appropriate and feasible, based on currently known data. Each precursor has a variable risk of progression culminating in its fully evolved, invasive melanoma.

DATA SOURCES.—

This review is based on the "Melanocytic Tumours" section of the 4th edition of the WHO Classification of Skin Tumours, published in 2018.

CONCLUSIONS.—

Melanomas were divided into those etiologically related to sun exposure and those that are not, as determined by their mutational signatures, anatomic site, and epidemiology. 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 basis of degree of associated solar elastosis. Low-CSD melanomas include superficial spreading melanomas and high-CSD melanomas incorporate lentigo maligna and desmoplastic melanomas. The "nonsolar" category includes acral melanomas, some melanomas in congenital nevi, melanomas in blue nevi, Spitz melanomas, mucosal melanomas, and uveal melanomas. The general term melanocytoma is proposed to encompass "intermediate" tumors that have an increased (though still low) probability of disease progression to melanoma.

Melanoma of the eyelid and periocular skin: Histopathologic classification and molecular pathology

Cutaneous melanoma, a potentially lethal malignancy of the periocular skin, represents only a small proportion of the roughly 87,000 new cases of cutaneous melanoma diagnosed annually in the United States. Most of our understanding of melanoma of the eyelid skin is extrapolated from studies of cutaneous melanoma located elsewhere. Recent years have witnessed major breakthroughs in molecular biology and genomics of cutaneous melanoma, some of which have led to the development of targeted therapies. The molecular insights have also kindled interest in rethinking how cutaneous melanomas are classified and assessed for risk. We provide a synopsis of the epidemiology, histopathologic classification, and clinical experience of eyelid melanoma since 1990 and then review major advances in the molecular biology of cutaneous melanoma, exploring how this impacts our understanding of classification and predicting risk.

Sentinel node metastasis mitotic rate (SN-MMR) as a prognostic indicator of rapidly progressing disease in patients with sentinel node-positive melanomas

Risk stratification of sentinel lymph node biopsy (SNB)-positive patients with malignant melanoma differs among current classification systems. To improve classification of patients with rapidly progressive disease who may profit from adjuvant therapy with novel immune or targeted treatment modalities, a single-center retrospective analysis was performed including all melanoma patients diagnosed with a positive SN at a university-based skin cancer center over a 10-year period (2002-2012) (96 of 419 patients). Sentinel node metastasis mitotic rate (SN-MMR) and further histologic parameters were determined by blinded histological re-evaluation and correlated with clinical follow-up (overall [OS], melanoma-specific [MSS], and disease-free survival [DFS]). Median follow-up was 53 months. In univariate analyses, SN tumor penetrative depth (TPD), maximum tumor diameter (MTD), number of positive SN, SN-MMR and the S-, Rotterdam, RDC, Hannover I and II classification systems correlated with OS, MSS and DFS. Multivariate Cox regression analyses showed that a binary classification system based only on the SN-MMR (<1 vs. ≥1 mitoses/mm2 ) was the strongest independent prognostic indicator for all endpoints analyzed. Kaplan-Meier analyses confirmed binary SN-MMR to be superior to stratify patients into high- and low-risk groups (45.45% vs. 87.92% 5-yr MSS). The general prognostic validity of the published SN classification systems was confirmed. The novel SN-MMR classification system may improve discrimination of patients with slowly and rapidly progressive disease. We therefore propose its implementation into clinical practice as the SN-MMR can be easily and reliably determined in routine pathology reports. Its prognostic value for the selection of patients amenable to adjuvant therapies should be studied in clinical trials.

Melanocytic Nevi in Malignant Melanomas

Background:

A substantial proportion of malignant melanomas arise in preexisting melanocytic nevi. However, the clinical and dermoscopic features of such combination lesions have not been well defined in the literature.

Objective:

To determine the ability to recognize in thin malignant melanomas the presence or absence of melanocytic nevi based on clinical and/or dermoscopic observations.

Methods:

Thirty malignant melanomas, less than 1 mm in Breslow thickness, were studied clinically, dermoscopically, and histologically for the presence or absence of features of a melanocytic nevus.

Results:

The ability to recognize melanocytic nevi within thin malignant melanomas was poor by clinical and dermoscopic examinations, with 30% false negatives and 23% false positives.

Conclusion:

One cannot depend on clinical and/or dermoscopic observations to rule out a melanocytic nevus within a thin malignant melanoma. Histopathologic study of a small portion of a combined melanocytic neoplasm could lead to the mistaken conclusion that the lesion is entirely a melanocytic nevus or entirely a malignant melanoma. Therefore, when feasible, lesions suspected of being malignant melanomas should be totally excised and step-sectioned throughout.

Tumor mitotic rate added to the equation: melanoma prognostic factors changed? : a single-institution database study on the prognostic value of tumor mitotic rate for sentinel lymph node status and survival of cutaneous melanoma patients

BACKGROUND

This study aimed to investigate the predictive value of the tumor mitotic rate per mm(2) (TMR) for sentinel lymph node (SLN) status and survival in intermediate and thick cutaneous melanoma.

METHODS

Patients treated for stage I and II melanoma with wide local excision and SLN biopsy between May 1995 and May 2013 were analyzed. In case of insufficient data regarding TMR, pathology slides were reanalyzed. Prognostic factors for SLN status and survival were analyzed with the emphasis on TMR, which was analyzed as a continuous variable, dichotomized (median value) and categorized by two methods.

RESULTS

The study analyzed 453 patients with complete TMR data. The median Breslow thickness was 2.20 mm, and 31.8 % of patients had tumor-positive sentinel lymph node biopsies (SLNBs). In the univariate analysis, TMR was associated with tumor-positive SLNB. This association was not significant in the multivariate analysis. Breslow thickness, primary tumor location on trunk and legs, and younger age were associated with tumor-positive SNLB. At a median follow-up of 47 months, 119 patients (26.3 %) had recurrent disease, and 92 (20.3 %) had died of melanoma. In the univariate analysis, TMR could be established as a significant prognostic factor for disease-free and disease-specific survival, but not in the multivariate analyses. Breslow thickness, ulcerated melanoma, and tumor-positive SLNB were significant prognostic factors for survival.

CONCLUSION

The study was unable to establish TMR as an independent prognostic factor associated with the presence of SLN metastasis. Regarding survival, increasing TMR showed a strong association with decreased survival in the univariate analysis, but this association was rendered nonsignificant by the importance of Breslow thickness and ulceration status in the multivariate model.

Assessment of tumor mitotic rate in primary cutaneous malignant melanomas 1 mm or less in thickness

BACKGROUND

Tumor mitotic rate in thin melanomas is recognized as a powerful, independent prognostic factor predicting survival. In nonulcerated cases, the presence of any dermal mitotic activity upstages the disease to pT1b. The extent to which tissue should be histologically examined to assess mitogenicity, however, has not been studied.

OBJECTIVE

We sought to determine whether in staging thin melanomas, there is a significant benefit in examining numerous tissue sections containing invasive disease.

METHOD

In all, 71 cases of thin cutaneous melanomas diagnosed between January 2012 and June 2013 were identified after a search performed on the Pathlab database. The slides were retrieved and reviewed retrospectively, comparing the identification of the first dermal tumor mitotic figure, if present, at 4 check-points: the first, third, fifth, or tenth tissue section examined.

RESULTS

A statistically significant difference in identification of the first dermal mitotic figure was found in examining 1 versus 3 tissue sections (P = .0411). No significant difference was found in examining numerous tissue sections.

LIMITATIONS

This was a retrospective study from a single institution with a limited number of participants.

CONCLUSION

In staging thin melanomas without ulceration, the optimal number of sections to assess is 3. No additional benefit is gained by examining numerous tissue sections.

Clinical and Histopathological Characteristics between Familial and Sporadic Melanoma in Barcelona, Spain

Background

About 6 to 14% of melanoma cases occur in a familial setting. Germline mutations in CDKN2A are detected in 20 to 40% of melanoma families.

Objective

To characterise the clinical and histopathological characteristics of familial melanoma thus providing more information to clinicians and contribute to the understanding of the genetic-environment interplay in the pathogenesis of melanoma.

Methods

Clinical, histological and immunohistochemical characteristics of 62 familial melanomas were compared with 127 sporadic melanomas.

Results

variables associated with familial melanoma were earlier age at diagnosis (OR 1.036; 95% CI 1.017–1.055), lower Breslow thickness (OR 1.288; 95% CI 1.013–1.683) and in situ melanomas (OR 2.645; 95% CI 1.211–5.778). Variables associated with CDKN2A mutation carriers were earlier age at diagnosis (OR 1.060; 95% CI 1.016–1.105), in situ melanomas (OR 6.961; 95% CI 1.895–25.567), the presence of multiple melanomas (OR 8.920; 95% CI 2.399–33.166) and the immunopositivity of the tumours for cytoplasmic survivin (OR 9.072; 95% CI 1.025–85.010).

Conclusions

Familial melanoma was significantly associated with the earlier age of onset, lower Breslow thickness and with a higher number of in situ melanomas; and also carriers of CDKN2A mutations were associated with a higher risk of multiple melanomas and cytoplasmic survivin immunostaining.

Impact of the 2009 (7th edition) AJCC melanoma staging system in the classification of thin cutaneous melanomas

CONTEXT

The 7th (2009) edition of the AJCC melanoma staging system incorporates tumor (Breslow) thickness, MR, and ulceration in stratifying T1 primary melanomas. Compared to the prior 6th (2001) edition, MR has replaced CL for thin melanomas.

OBJECTIVE

We sought to identify and report differences of the classification of thin melanomas as well as outcome of SLNB in patients according to the 6th and 7th editions at our institution.

RESULTS

106 patients were identified with thin melanomas verified by wide excision. 31 of 106 thin melanomas were reclassified according to the 7th edition of the AJCC. Of those 31, 15 CL II/III patients (6th edition T1a) were reclassified as T1b based on the presence of mitoses while 16 CL IV patients (6th edition T1b) were categorized as T1a based on the absence of mitoses. 26/31 reclassified patients underwent SLNB, and all were negative. Patients with thin melanoma and a +SLNB (N = 3) were all classified as T1b according to both staging systems.

CONCLUSIONS

In our experience, 29% of thin melanomas were reclassified according to the 7th edition with similar proportions of patients re-distributed as T1a (14%) and T1b (15%). Cases with +SLN corresponded with T1b lesions in both 6th and 7th editions.

Histological and genetic evidence for a variant of superficial spreading melanoma composed predominantly of large nests

Cutaneous melanomas are characterized by a range of histological appearances, and several morphological variants have been described. In this study, we report a variant of superficial spreading melanoma that is characterized by large, irregular junctional melanocytic nests. The junctional nests varied in shape and size, showed focal tendency to confluence, and were often surrounded by a cuff of epidermal keratinocytes. The melanocytes comprising the nests showed variable cytological atypia. In most of the cases, scant intraepidermal or junctional single melanocytes were seen, and other well-documented diagnostic criteria for melanoma were lacking, and as a result, histological recognition of these tumors as melanoma was difficult. Some cases were associated with an invasive dermal component or showed evidence of sun damage. To provide supporting evidence for malignancy, we analyzed these tumors for genomic aberrations. Using array comparative genomic hybridization (aCGH), we identified multiple genomic aberrations in all analyzed cases. A similar pattern of genomic aberrations was seen in a control group of bona fide superficial spreading melanomas, suggesting that these 'melanomas composed exclusively or predominantly of large nests' are indeed variants of superficial spreading melanoma. Fluorescence in-situ hybridization (FISH) was positive in 40% of the cases. However, using aCGH, the FISH-negative cases showed multiple genomic aberrations in regions that are not covered by FISH. The low sensitivity of the FISH test can be explained by the fact that FISH only evaluates four genomic loci for aberrations, whereas aCGH surveys the entire genome. In summary, we present histological and molecular genetic evidence for a morphological variant of superficial spreading melanoma. Awareness of the histological features will aid in their correct diagnosis as melanoma, and in difficult cases, judicious application of ancillary tests such as aCGH (rather than FISH) will assist accurate diagnosis.

Biomarkers as key contributors in treating malignant melanoma metastases

Melanoma is a human neurocristopathy associated with developmental defects in the neural crest-derived epidermal melanocytes. At the present time, at least three hypotheses were identified that may explain melanoma aetiology, as follows: (1) a model of linear progression from differentiated melanocytes to metastatic cancer cells (2) a model involving the appearance of melanoma stem-like cells, and (3) an epigenetic progenitor model of cancer. Treating metastatic melanoma is one of the most serious challenges in the 21st century. This is justified because of a subpopulation of cells presenting a remarkable molecular heterogeneity, which is able to explain the drug resistance and the growing mortality rates worldwide. Fortunately, there are now evidences sustaining the importance of genetic, epigenetic, and metabolomic alterations as biomarkers for classification, staging, and better management of melanoma patients. To illustrate some fascinating insights in this field, the genes BRAF^V600E and CTLA4 have been recognized as bona fide targets to benefit melanoma patients. Our research attempts to carefully evaluate data from the literature in order to highlight the link between a molecular disease model and the key contribution of biomarkers in treating malignant melanoma metastases.

Lentigo Maligna: Melanoma In Situ on Chronically Sun-Damaged Skin

Context.—Cutaneous primary invasive malignant melanoma often is classified by its histologic appearance. Major recognized histologic subtypes of melanoma include superficial spreading, lentigo maligna melanoma, nodular, and acral lentiginous. More recently, it has been shown that most primary invasive melanomas harbor nonrandom genetic or biochemical aberrations that correlate with anatomic site or with the amount of cutaneous exposure to sunlight. It also is generally accepted that most primary invasive melanomas are preceded by an intraepidermal atypical melanocytic proliferation that lacks invasive capability (melanoma in situ).

Objective.—To focus on lentigo maligna, the preinvasive/in situ form of melanoma located on chronically sun-damaged skin.

Data Sources.—Review of the literature and the authors' personal experiences.

Conclusions.—A better understanding of the earliest stage of melanoma progression, including the contribution of chronic exposure to ultraviolet radiation, may lead to improved classification schemes that direct more effective targeted or personalized therapies for patients.

Prognostic significance of mitotic rate in localized primary cutaneous melanoma: an analysis of patients in the multi-institutional American Joint Committee on Cancer melanoma staging database

PURPOSE

The aim of this study was to assess the independent prognostic value of primary tumor mitotic rate compared with other clinical and pathologic features of stages I and II melanoma.

METHODS

From the American Joint Committee on Cancer (AJCC) melanoma staging database, information was extracted for 13,296 patients with stages I and II disease who had mitotic rate data available.

RESULTS

Survival times declined as mitotic rate increased. Ten-year survival ranged from 93% for patients whose tumors had 0 mitosis/mm(2) to 48% for those with ≥ 20/mm(2) (P < .001). Mean number of mitoses/mm(2) increased as the primary melanomas became thicker (1.0 for melanomas ≤ 1 mm, 3.5 for 1.01 to 2.0 mm, 7.3 for 3.01 to 4.0 mm, and 9.6 for > 8 mm). Ulceration was also associated with a higher mitotic rate; 59% of ulcerated melanomas had ≥ 5 mitoses/mm(2) compared with 16% of nonulcerated melanomas (P < .001). In a multivariate analysis of 10,233 patients, the independent predictive factors for survival in order of statistical significance were as follows: tumor thickness (χ(2) = 104.9; P < .001), mitotic rate (χ(2) = 67.0; P < .001), patient age (χ(2) = 48.2; P < .001), ulceration (χ(2) = 46.4; P < .001), anatomic site (χ(2) = 34.6; P < .001), and patient sex (χ(2) = 33.9; P < .001). Clark level of invasion was not an independent predictor of survival (χ(2) = 3.2; P = .37).

CONCLUSION

A high mitotic rate in a primary melanoma is associated with a lower survival probability. Among the independent predictors of melanoma-specific survival, mitotic rate was the strongest prognostic factor after tumor thickness.

Evolving concepts in melanoma classification and their relevance to multidisciplinary melanoma patient care

In the initial period after melanoma was recognised as a disease entity in the early 1800's, it was subclassified on the basis of its presumed origin (from a precursor naevus, from a melanocytic precursor lesion acquired during adult life or in previously blemish-fee skin). In 1967 the eminent American pathologist, Dr Wallace Clark, proposed a histogenetic classification for melanoma in which the disease was subdivided predominantly on the basis of histopathological features of the intra-epidermal component of the tumour adjacent to any dermal invasive component. The subtypes were superficial spreading melanoma (SSM), lentigo maligna melanoma (LMM) and nodular melanoma (NM). Whilst additional entities, including acral lentiginous melanoma, mucosal melanoma, desmoplastic melanoma and naevoid melanoma have since been recognised, SSM, LMM and NM remain in the latest (2006) version of the WHO melanoma classification. Clark's histogenetic classification has been criticised because the criteria upon which it is based include clinical features (such as the site of the melanoma) and non-tumourous histopathological features (such as the character of the associated epidermis and the degree of solar elastosis) and also because of overlap in defining features, lack of an independent association with patient outcome and minimal relevance as a determinant of clinical management. However, such criticisms fail to acknowledge its importance in highlighting the myriad of clinical and histological guises of melanoma, which if not recognized by clinicians and pathologists will inevitably lead to a delay in diagnosis and a concomitant adverse clinical outcome. Recently, mutually exclusive oncogenic mutations in melanomas involving NRAS (15-20%), BRAF (50%), CKIT (2%), and GNAQ/GNA11 (50% of uveal melanomas) have been identified. This might herald the beginning of a new molecular classification of melanoma in which the biologically distinct subsets share a common oncogenic mechanism, behave clinically in a similar fashion and require similar clinical management. These discoveries are already being successfully exploited as therapeutic targets in clinical trials of metastatic melanoma patients with promising activity. Whilst there remains much to be discovered in this rapidly evolving field, there is already great optimism that more rational and effective therapies for melanoma patients will soon be widely available.

Lentiginous Melanoma

Context.—Atypical lentiginous melanocytic lesions, particularly in older individuals, continue to pose a diagnostic challenge. Such lesions often show features intermediate between lentiginous nevus and melanoma in situ. We have recently defined within this group of lesions a histologic pattern of lentiginous melanoma, a slowly progressing variant of melanoma typically found on the trunk and proximal extremities of middle-aged and older individuals.

Objective.—To review the clinical and histologic features of lentiginous melanoma and its histologic differential diagnosis.

Data Sources.—Review of pertinent published literature and work in our laboratory.

Conclusions.—Lentiginous melanoma defines a subset of slowly progressing melanoma occurring in middle-aged and older patients. It is histologically characterized by a broad atypical lentiginous growth pattern of moderately atypical melanocytes showing focal nesting and pagetoid spread without significant dermal fibroplasia or alteration of the rete ridges. Lentiginous melanoma shows significant overlap in clinical and histologic features with atypical lentiginous nevus (of the elderly). Relationship between these entities requires further investigations. Given the risk of progression to invasive melanoma, all lesions showing features of lentiginous melanoma should be treated with adequately wide excision.

Useof anti-phosphohistone H3 immunohistochemistry to determine mitotic rate in thin melanoma

The seventh edition of the American Joint Committee on Cancer (AJCC) melanoma staging system, slated for release in 2010, will introduce mitotic rate (MR) as one of the primary criteria for staging thin melanoma (< or = 1.0 mm). Accurate counts are essential because the finding of a single mitotic figure (MF) will alter the staging and management of these patients. The traditional manner of counting of mitotic figures (MFs) using a X40 objective is time consuming and prone to inter- and intraobserver variability. We employed an antibody to phosphohistone H3 (pHH3, ser10) that labels MFs in all stages of mitosis, to evaluate mitotic counts at X20 in tissue sections from 30 melanoma patients with thin lesions 0.45 to 1.2 mm in depth, and compared results with routine hematoxylin and eosin (H&E) in a double-blind fashion. The mean MR was 1.63 by antipHH3, and 0.67 for H&E, representing a mean increase of 243%. The Spearman correlation coefficient for MR in H&E and anti-pHH3 sections was 0.88 (P < 0.0001). When melanomas were designated as "mitotically active," if the MR by anti-pHH3 was > or = 2 and > or = 1 by H&E, the correlation coefficient increased to 1.0. No thin melanomas were mitotically inactive on anti-pHH3 but active on H&E. Results indicate that anti-pHH3 is a useful immunostain for labeling melanocytes in mitosis. Subsequent studies will be needed confirm the accuracy of this staining technique, which has the potential to be used as a screening method for counting MFs before conventional H&E methodology in the microstaging of thin melanoma.

Treatment of cutaneous melanoma: current approaches and future prospects

Melanoma is the most aggressive and deadly type of skin cancer. Surgical resection with or without lymph node sampling is the standard of care for primary cutaneous melanoma. Adjuvant therapy decisions may be informed by careful consideration of prognostic factors. High-dose adjuvant interferon alpha-2b increases disease-free survival and may modestly improve overall survival. Less toxic alternatives for adjuvant therapy are currently under study. External beam radiation therapy is an option for nodal beds where the risk of local recurrence is very high. In-transit melanoma metastases may be treated locally with surgery, immunotherapy, radiation, or heated limb perfusion. For metastatic melanoma, the options include chemotherapy or immunotherapy; targeted anti-BRAF and anti-KIT therapy is under active investigation. Standard chemotherapy yields objective tumor responses in approximately 10%-20% of patients, and sustained remissions are uncommon. Immunotherapy with high-dose interleukin-2 yields objective tumor responses in a minority of patients; however, some of these responses may be durable. Identification of activating mutations of BRAF, NRAS, c-KIT, and GNAQ in distinct clinical subtypes of melanoma suggest that these are molecularly distinct. Emerging data from clinical trials suggest that substantial improvements in the standard of care for melanoma may be possible.

Treatment of cutaneous melanoma: current approaches and future prospects

Melanoma is the most aggressive and deadly type of skin cancer. Surgical resection with or without lymph node sampling is the standard of care for primary cutaneous melanoma. Adjuvant therapy decisions may be informed by careful consideration of prognostic factors. High-dose adjuvant interferon alpha-2b increases disease-free survival and may modestly improve overall survival. Less toxic alternatives for adjuvant therapy are currently under study. External beam radiation therapy is an option for nodal beds where the risk of local recurrence is very high. In-transit melanoma metastases may be treated locally with surgery, immunotherapy, radiation, or heated limb perfusion. For metastatic melanoma, the options include chemotherapy or immunotherapy; targeted anti-BRAF and anti-KIT therapy is under active investigation. Standard chemotherapy yields objective tumor responses in approximately 10%-20% of patients, and sustained remissions are uncommon. Immunotherapy with high-dose interleukin-2 yields objective tumor responses in a minority of patients; however, some of these responses may be durable. Identification of activating mutations of BRAF, NRAS, c-KIT, and GNAQ in distinct clinical subtypes of melanoma suggest that these are molecularly distinct. Emerging data from clinical trials suggest that substantial improvements in the standard of care for melanoma may be possible.

Beyond BRAF in melanoma

Recent progress in the analysis of genetic alterations in melanoma has identified recurrent mutations that result in the activation of critical signaling pathways promoting growth and survival of tumors cells. Alterations in the RAS-RAF-MAP kinase and PI3-kinase signaling pathways are commonly altered in melanoma. Mutations in BRAF, NRAS, KIT, and GNAQ occur in a mutually exclusive pattern and lead to MAP-kinase activation. Loss of PTEN function, primarily by deletion, is the most common known genetic alteration in the PI3-kinase cascade, and is commonly associated with BRAF mutations (Curtin et al., N Engl J Med 353:2135-2147, 2005; Tsao et al., Cancer Res 60:1800-1804, 2000, J Investig Dermatol 122:337-341, 2004). The growth advantage conveyed by the constitutive activation of these pathways leads to positive selection of cells that have acquired the mutations and in many instances leads to critical dependency of the cancer cells on their activation. This creates opportunities for therapeutic interventions targeted at signaling components within these pathways that are amenable for pharmacological inhibition. This concept follows the paradigm established by the landmark discovery that inhibition of the fusion kinase BCR-ABL can be used to treat chronic myelogenous leukemia (Druker et al., N Engl J Med 344:1031-037, 2001). The review will focus primarily on kinases involved in signaling that are currently being evaluated for therapeutic intervention in melanoma.

Divergent cancer pathways for early-onset and late-onset cutaneous malignant melanoma

BACKGROUND

Emerging data suggest that cutaneous malignant melanomas (CMM) may arise through divergent cancer pathways that are linked to intermittent versus accumulated sun exposure. However, numerous questions remain regarding the timing and/or age of exposure.

METHODS

The authors systematically examined the effect of aging on CMM incidence in data from the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute. Standard descriptive epidemiology was supplemented with mathematical models. The impact of advancing age on CMM incidence was assessed by sex, histopathologic classification (superficial spreading melanoma [SSM] or lentigo maligna melanoma [LMM]), and anatomic site (face, head, and neck [FHN] or lower extremity [LE]).

RESULTS

Sex, histopathology, and anatomic site were age-specific effect modifiers for CMM that indicated divergent (bimodal) early-onset and late-onset cancer pathways. Early-onset melanomas were associated predominantly with women, SSM, and LE. Late-onset melanomas were correlated with men, LMM, and FHN. Early- and late-onset melanoma populations were confirmed with age-period-cohort models that were adjusted for period and cohort effects. Two-component mixture models also fit the data better than a single cancer population.

CONCLUSIONS

The current results were consistent with a divergent and age-dependent solar hypothesis for CMM. Early-onset melanomas may represent gene-sun exposure interactions that occur early (and/or intermittently) in life among susceptible individuals. Late-onset melanomas may reflect accumulated, lifelong sun exposure in comparatively less susceptible individuals. Future analytical studies should be powered adequately to account for this age-dependent effect modification both for acknowledged melanoma risk factors (sex, histopathology, and anatomic site) and for suspected melanoma risk factors, such as constituent genetic variants.

The classification of cutaneous melanoma

Forty years ago, a clinical and histological classification scheme and prognostic factors were described for cutaneous melanoma. This scheme included the subtypes superficial spreading, nodular and lentigo maligna, and prognostic factors including tumor thickness, ulceration, and mitotic activity. There have been some tweaks to the classification scheme, but these basic findings form the foundation for melanoma diagnosis and staging today. Currently, no molecular marker or target has proved reliably useful in the staging or treatment of melanoma. Measurement with a simple ruler serves as the basis for the staging of primary cutaneous melanoma, while the recognition of primary tumor mitotic activity and ulceration also remain significant factors. Recently, mutational analysis has revealed a correlation of activating mutations with the morphological descriptors from decades ago. Future classification schemes may have more power in predicting response to therapy by integrating specific genomic and intra-tumoral expression profiles with histologic findings.

Angiotropism is an independent predictor of local recurrence and in-transit metastasis in primary cutaneous melanoma

The migration of melanoma cells along the external surface of blood vessels (angiotropism) has recently been proposed as a mechanism for melanoma metastasis (termed extravascular migratory metastasis). To determine whether the presence of angiotropism, as seen in the routine hematoxylin and eosin sections of primary cutaneous melanomas (PCMs), predicts the development of local or in-transit melanoma recurrence, 32 patients with a PCM who developed local or in-transit recurrence were matched for Breslow thickness with 59 "control" patients with a PCM who did not. The slides from both groups of patients were analyzed in a "blinded" manner for evidence of angiotropism. Other histologic and clinical variables were also assessed. Angiotropism was found more often in patients who developed local or in-transit recurrence (cases) compared with those patients who did not (controls) (P=0.02). Variables that showed a statistically significant association with angiotropism on univariate analysis were: increasing Breslow thickness (P<0.0001), greater Clark level (P<0.001), increasing mitotic index (P<0.0001), presence of ulceration (P<0.01), and absence of regression (P<0.05). The median disease-free survival was 72 months for patients with angiotropism and 104 months for those without (P=0.02). On multivariate analysis the presence of angiotropism was an independent predictor of decreased disease-free survival (P=0.02). This is the first reported study to identify a statistically significant association between the development of local or in-transit recurrence of PCM and the histologic presence of angiotropism and that angiotropism is an independent predictor of decreased disease-free survival, as far as we are aware. Our findings support the hypothesis that angiotropism represents a pathogenic mechanism for metastasis in patients with PCM.

Improving melanoma classification by integrating genetic and morphologic features

BACKGROUND

In melanoma, morphology-based classification systems have not been able to provide relevant information for selecting treatments for patients whose tumors have metastasized. The recent identification of causative genetic alterations has revealed mutations in signaling pathways that offer targets for therapy. Identifying morphologic surrogates that can identify patients whose tumors express such alterations (or functionally equivalent alterations) would be clinically useful for therapy stratification and for retrospective analysis of clinical trial data.

METHODOLOGY/PRINCIPAL FINDINGS

We defined and assessed a panel of histomorphologic measures and correlated them with the mutation status of the oncogenes BRAF and NRAS in a cohort of 302 archival tissues of primary cutaneous melanomas from an academic comprehensive cancer center. Melanomas with BRAF mutations showed distinct morphological features such as increased upward migration and nest formation of intraepidermal melanocytes, thickening of the involved epidermis, and sharper demarcation to the surrounding skin; and they had larger, rounder, and more pigmented tumor cells (all p-values below 0.0001). By contrast, melanomas with NRAS mutations could not be distinguished based on these morphological features. Using simple combinations of features, BRAF mutation status could be predicted with up to 90.8% accuracy in the entire cohort as well as within the categories of the current World Health Organization (WHO) classification. Among the variables routinely recorded in cancer registries, we identified age < 55 y as the single most predictive factor of BRAF mutation in our cohort. Using age < 55 y as a surrogate for BRAF mutation in an independent cohort of 4,785 patients of the Southern German Tumor Registry, we found a significant survival benefit (p < 0.0001) for patients who, based on their age, were predicted to have BRAF mutant melanomas in 69% of the cases. This group also showed a different pattern of metastasis, more frequently involving regional lymph nodes, compared to the patients predicted to have no BRAF mutation and who more frequently displayed satellite, in-transit metastasis, and visceral metastasis (p < 0.0001).

CONCLUSIONS

Refined morphological classification of primary melanomas can be used to improve existing melanoma classifications by forming subgroups that are genetically more homogeneous and likely to differ in important clinical variables such as outcome and pattern of metastasis. We expect this information to improve classification and facilitate stratification for therapy as well as retrospective analysis of existing trial data.

Treatment and prognosis of malignant melanoma of the oral cavity: preoperative surgical procedure increases risk of distant metastasis

OBJECTIVE

Many authors have reported that oral melanoma patients showed much worse prognosis than those with cutaneous melanoma. We investigated treatment method and prognosis of patients with oral malignant melanoma.

STUDY DESIGN

Twenty-one patients with oral melanoma treated at our hospital were investigated, with special reference to the influence of preoperative surgical procedures such as biopsy, incision, or tooth extraction on the prognosis.

RESULTS

All patients underwent surgery followed by immuno-chemotherapy with dimethyl triazeno imidazole carboxamide (DTIC), ninustine hydrochloride (ACNU), vincristine (VCR), and biologic response modifier OK-432. Local control was obtained in 20 of 21 patients. Lymph node metastasis appeared in 13 patients, but neck failure was not detected in any patients. Distant metastasis occurred in 9 patients in spite of loco-regional control. Five-year survival rate of 12 patients with no preoperative surgical procedure was 91.7%, while that of the 9 patients who had undergone surgical procedures before treatment was 25.9% (P < .05).

CONCLUSIONS

Oral melanoma patients can obtain a prognosis as good as that for cutaneous melanoma patients, when the above-mentioned therapy is used without any preoperative surgical procedures.

Distribution of clinical-pathological types of cutaneous melanomas and mortality rate in the region of Passo Fundo, RS, Brazil

OBJECTIVE

To describe the characteristics of all cases of primary cutaneous melanoma during the period 1995-2001, registered at pathology departments in the region of Passo Fundo.

METHODS

The sample studied consisted of 229 primary cutaneous melanoma lesions, identified by anatomopathological reports, in 218 patients. The variables evaluated were: sex, age, anatomical site, histological type, level of invasion and tumor thickness. The rate of incidence, mortality and survival curve were calculated.

RESULTS

The most frequent tumor site was in the back of men (49.5%) and in the lower limbs of women (33.1%). The most frequent clinical-pathological type for both sexes was the superficial expansive type (superficial spreading) at 61.6%. The level of invasion was higher in men, using Clark level III (30.3%), than in women. In women the most frequent level of invasion was Clark level II (33.1%). Of the total number of lesions, 198 (47.2%) were </= 1 mm thick, and 23.2% of the men had thicker lesions (> 4 mm) than the women. The incidence was 5.67 per 100,000 patients-year during this period and the mortality rate was 2.16 per 100,000 patients-year.

CONCLUSIONS

In the sample studied the most common sites were in the back of men and in the legs of women. The predominant type clinical-pathological was superficial spreading.

Melanocytic nevi simulant of melanoma with medicolegal relevance

A group of melanocytic benign nevi are prone to be misdiagnosed as nodular or superficial spreading melanoma. This review illustrates the most frequent forms of these nevi in direct comparison with their malignant morphologic counterparts. The nevi are: hyper-cellular form of common nevus to be distinguished from nevoid melanoma, Spitz nevus (vs spitzoid melanoma), Reed nevus (vs melanoma with features of Reed nevus), cellular atypical blue nevus (vs melanoma on blue nevus), acral nevus (vs acral melanoma), Clark dysplastic nevus (vs superficial spreading melanoma), desmoplastic nevi (vs desmoplastic melanoma), benign proliferative nodules in congenital nevi (vs melanoma on congenital nevi), epithelioid blue nevus (vs animal type melanoma) and regressed nevus (vs regressed melanoma). For each single 'pair' of morphological look-alikes, a specific set of morphological, immunohistochemical and genetic criteria is provided.

Malignant melanoma in the 21st century, part 2: staging, prognosis, and treatment

Critical to the clinical management of a patient with malignant melanoma is an understanding of its natural history. As with most malignant disorders, prognosis is highly dependent on the clinical stage (extent of tumor burden) at the time of diagnosis. The patient's clinical stage at diagnosis dictates selection of therapy. We review the state of the art in melanoma staging, prognosis, and therapy. Substantial progress has been made in this regard during the past 2 decades. This progress is primarily reflected in the development of sentinel lymph node biopsies as a means of reducing the morbidity associated with regional lymph node dissection, increased understanding of the role of neoangiogenesis in the natural history of melanoma and its potential as a treatment target, and emergence of innovative multimodal therapeutic strategies, resulting in significant objective response rates in a disease commonly believed to be drug resistant. Although much work remains to be done to improve the survival of patients with melanoma, clinically meaningful results seem within reach.

Malignant melanoma in the 21st century, part 1: epidemiology, risk factors, screening, prevention, and diagnosis

Malignant melanoma is an aggressive, therapy-resistant malignancy of melanocytes. The incidence of melanoma has been steadily increasing worldwide, resulting in an increasing public health problem. Exposure to solar UV radiation, fair skin, dysplastic nevi syndrome, and a family history of melanoma are major risk factors for melanoma development. The interactions between genetic and environmental risk factors that promote melanomagenesis are currently the subject of ongoing research. Avoidance of UV radiation and surveillance of high-risk patients have the potential to reduce the population burden of melanoma. Biopsies of the primary tumor and sampling of draining lymph nodes are required for optimal diagnosis and staging. Several clinically relevant pathologic subtypes have been identified and need to be recognized. Therapy for early disease is predominantly surgical, with a minor benefit noted with the use of adjuvant therapy. Management of systemic melanoma is a challenge because of a paucity of active treatment modalities. In the first part of this 2-part review, we discuss epidemiology, risk factors, screening, prevention, and diagnosis of malignant melanoma. Part 2 (which will appear in the April 2007 issue) will review melanoma staging, prognosis, and treatment.

Factores pronósticos en el melanoma maligno cutáneo localizado: estudio de 639 pacientes

BACKGROUND AND OBJECTIVE

Several clinical and histological prognostic factors have been identified in localized melanoma. However, further studies with better defined and more reproducible histological parameters are needed. Our aim was to identify the prognostic factors for survival in cutaneous melanoma in the Spanish population.

PATIENTS AND METHOD

Six hundred and thirty nine patients with localized melanoma, stages I and II of the last version of the American Joint Committee on Cancer staging system for cutaneous melanoma, with 2 years of follow-up or documented relapse, were selected from the database of the Department of Dermatology. Univariate and multivariate Cox regression analyses were performed for overall and disease free survival.

RESULTS

Tumor thickness appeared as the most important prognostic factor for both overall and disease free survival in the multivariate analysis. Inflammatory infiltrate and sex were only significant for overall survival, and location, age and ulceration were significant for disease free survival. Other variables, such as histological type, mitotic rate or level of invasion, lost their prognostic significance in the multivariate analysis.

CONCLUSIONS

Tumor thickness is the most important prognostic factor to predict survival in localized melanoma. Other factors such as sex, inflammatory infiltrate, location, age or ulceration, have also an important role in prognosis.

Histopathological characteristics of malignant melanoma affecting mucous membranes: a unifying concept of histogenesis

AIMS

To investigate histopathological characteristics of melanocytic lesions affecting mucous membranes in various anatomical sites. Particular attention was paid to elucidation of morphological characteristics of early phases of mucosal melanoma in order to contribute to effective detection of this highly malignant neoplasm in the curable stages.

METHODS

A total of 87 melanocytic lesions of mucous membranes were investigated histopathologically. There were 55 malignant melanomas including eight lesions of melanoma in situ, three in the radial growth phase (RGP) and 44 in the vertical growth phase (VGP), and 28 benign melanocytic lesions including four melanotic macules, 19 melanocytic naevi and five blue naevi. In addition, this series also included four equivocal lesions for which diagnoses were not definitely determined. With regard to malignant melanoma, histopathological patterns of in situ phase and RGP were intensely evaluated.

RESULTS

Histopathological features of benign melanocytic lesions were essentially the same as those of the corresponding lesions of the skin. In the vast majority of mucosal melanomas, irrespective of anatomical sites, the main histopathological pattern seen in melanoma in situ and in RGP was the lentiginous pattern, which shows proliferation of atypical melanocytes in the lower layer of more or less acanthotic epithelium, though subtle variations of the pattern were detected. No association of melanocytic naevus was detected in any cases of melanoma. Based on these findings, we have proposed a unifying concept of de novo histogenesis of mucosal malignant melanoma.

CONCLUSIONS

Our concept of histogenesis of mucosal melanoma assists in the identification of this highly malignant neoplasm in the early curable stages.

Oral mucosal melanoma: a series of case reports

INTRODUCTION

Due to the rarity of oral malignant melanomas case reports are a necessary source of information. Ten new cases are reported with a minimum follow-up of 3 years.

PATIENTS AND METHODS

Patients were treated during a period of 10 years. Clinical, demographic and pathologic findings were examined.

RESULTS

In 6 males (60%) and 4 females with a mean age of 64.3 years the tumour locations were: hard palate-maxillary gingiva (3 cases), maxillary gingiva (2), lower gingiva (2), tongue (2), hard/soft palate-buccal mucosa (1). Pre-existing melanotic pigmentation had been present in 4 patients. Four patients were in stage I, 5 in stage II, and 1 in stage III. Surgical excision was the primary treatment in 9 cases. Five patients underwent simultaneous neck dissections. All patients received radiation and multimode adjuvant therapies. After a 3-year follow-up 3 patients are still alive (50% (2/4) of those presenting in stage I and 20% (1/5) in stage II).

CONCLUSIONS

Due to the rarity of oral melanoma, individual experience is limited. The poor prognosis and the different treatments reflect this situation.

Clinical and histopathological characterization of cutaneous melanomas in the melanoblastoma-bearing Libechov minipig model

Spontaneous animal tumors appear to be highly suitable models to study human oncology and cancer therapy. The aim of this study was to characterize the clinical and histological features of hereditary melanocytic lesions found in the French herd of melanoblastoma-bearing Libechov minipigs (MeLiM) and their Duroc crossbreeds. Clinically, we discriminated between three types of melanocytic skin lesions, which offer a lesion continuum from lentigo to metastatic melanomas. More than 70% of these lesions appear on piglets before they are 3 months old and preferentially on homogeneous black coat piglets. The incidence of melanoma reaches 50% in MeLiM. Most of the highly invasive melanomas regressed spontaneously in the first year of the piglet's life and the regression was followed by hair, skin and iris depigmentation. A histopathological study was conducted according to the human melanoma classification. Except for lentigo maligna, we observed the three main types of human melanoma in swine [superficial spreading melanoma (SSM), nodular or unclassified melanoma] with an excess of SSM (59-67%). The histological events leading to total spontaneous regression are chronologically described. The genetic predisposition, the high incidence of melanoma, the clinical and histopathological features similar to the human disease and the high rate of spontaneous regression offer an opportunity to use this model for studying genetic events controlling melanoma development and regression and the biological mechanisms involved in oncogenesis and anti-cancerous self-defense.

Comparative genomic hybridization analysis of hereditary swine cutaneous melanoma revealed loss of the swine 13q36-49 chromosomal region in the nodular melanoma subtype

Genetic alterations implicated in malignant melanoma are still poorly understood. Malignant melanomas present highly variable histologic and cytologic patterns. The aim of the present study is to define genomic imbalances associated with the development of 2 histologic types of swine hereditary cutaneous melanoma. We have investigated 11 swine tumors by comparative genomic hybridization (CGH), 4 superficial spreading melanomas (SSMs) and 7 nodular melanomas (NMs). Following laser capture microdissection and degenerate oligonucleotide primed-polymerase chain reaction, we were able to isolate and then amplify DNA from the 2 histologic subtypes. Consensus regions of chromosome gains were identified on both histologic subtypes, on swine chromosomes 3p13-p17 (75% of the SSMs and 71% of the NMs), 12q (100% of the SSMs and 57% of the NMs) and 14q11-q21 (75% of the SSMs and 42% of NMs). Chromosomal loss was restricted to NM lesions and the swine 13q36-49 region was lost in 100% of the NMs. Interphase fluorescence in situ hybridization with a probe mapping to the 13q41-q42 region indicates loss of the corresponding region on NM lesions. Taking into account this CGH analysis and the comparative genomic data between swine and human genomes, we suggest that a role for the human chromosomes 3p11-qter and chromosome 21 losses should be investigated in human nodular melanoma progression.