Inter-observer variation between pathologists in the classification of cutaneous malignant melanoma in western Australia

Interobserver Variability in the Histopathological Evaluation of Melanoma: Analysis of 60 Cases

INTRODUCTION

Since the field of dermatopathology is not an exact science, it is subject to personal subjectivity, which sometimes causes disagreements on the diagnosis and assessment of some histological features. In the case of melanoma, some variables such as regression are associated with low interobserver agreement. On the contrary, other variables such as the measurement of Breslow thickness show high reproducibility.

OBJECTIVE

The main objective of our study was to investigate multiple features of 60 consecutive cases of melanoma to establish interobserver reproducibility.

METHODS AND MAIN RESULTS

We conducted an observational and descriptive study at Hospital de Manises, Valencia, Spain, IVO Foundation, Valencia, Spain, and Hospital 12 de Octubre, Madrid, Spain. The mean level of agreement of all study variables was moderate (Cohen's kappa coefficient statistic=0.5). The highest agreement corresponded to polypoid morphology, pigmentation, ulceration, and solar elastosis. On the other hand, the lowest level agreement was reached for the presence of cellular pleomorphism and tumor necrosis.

CONCLUSIONS

Our mean level of agreement was moderate, which reflects that some of the measured characteristics such as cellular pleomorphism or the presence of necrosis cannot be used for future studies or must be redefined and their reproducibility, reestablished. When conducting a research study, it is necessary to analyze the study variables to demonstrate their validity to measure or classify a certain feature. It is also advisable to warrant that that the variables are reproducible to be able to use them for other studies or in the routine clinical practice.

Discordance in Diagnosis of Melanocytic Lesions and Its Impact on Clinical Management

CONTEXT.—

Accurate diagnosis of melanocytic lesions is fundamental for appropriate clinical management.

OBJECTIVE.—

To evaluate the degree of discordance, if any, between histopathologic diagnoses of melanocytic lesions at referring institutions and at a tertiary referral cancer center and the potential impact of such discordance on clinical management.

DESIGN.—

We retrospectively identified all patients referred to our comprehensive cancer center for evaluation of a melanocytic lesion from January 2010 to January 2011. For each patient, the histopathologic diagnosis from the referring institution was compared with the histopathologic diagnosis from a dermatopathologist at our center. Discordances were classified as major if they resulted in a change in clinical management and minor if they did not.

RESULTS.—

A total of 1521 cases were included. The concordance rates were 72.2% (52 of 72) for dysplastic nevus, 75.0% (15 of 20) for all other types of nevi, 91.1% (143 of 157) for melanoma in situ, 96.1% (758 of 789) for invasive melanoma, and 99.6% (478 of 480) for metastatic melanoma. Major discordances were found in 20.2% of cases (307 of 1521), and minor discordances were found in 48.8% of cases (742 of 1521). Compared with the guideline-based treatment recommendation based on the referring-institution diagnosis, the guideline-based treatment recommendation based on the cancer center diagnosis was more extensive in 5.9% (89 of 1521) of patients and less extensive in 5.0% (76 of 1521) of patients.

CONCLUSIONS.—

Our findings underscore the importance of secondary histopathologic review of melanocytic lesions by expert dermatopathologists because significant changes in the diagnosis, tumor classification, and/or staging may be identified; thus, resulting in critical changes in recommendations for clinical management.

Global and mitosis-specific interobserver variation in mitotic count scoring and implications for malignant melanoma staging

AIMS

Staging is the gold standard for predicting malignant melanoma outcome but changes in its criteria over time indicate ongoing evolution. One notable recent change from the 8th edition of the American Joint Committee on Cancer (AJCC) staging manual was removal of mitotic count. We explore the extent to which this feature is limited by interobserver error in order to find ways to improve its fitness for use should it be revisited in future staging versions.

METHODS AND RESULTS

In a cohort of 476 patients with melanoma ≤1.0 mm, a mitotic count of 0 versus 1 was significant for metastasis-free survival, but not melanoma-specific or overall survival. In 10 melanomas that were 0.9-1.0 mm thick, the mitotic count intraclass correlation coefficient for histopathologists was 0.58 (moderate agreement). Uniquely, we also assessed agreement for specific putative mitotic figures, identifying precise reasons why specific mitotic figures qualified for scoring or elimination. A kappa score was 0.54 (moderate agreement). We also gathered data on other staging features. Breslow thickness had an intraclass correlation coefficient of 0.41 (moderate agreement) and there was a systematic difference between histopathologists among cases (P = 0.04). Every case had a range that crossed the AJCC8 0.8-mm pT1a/pT1b staging boundary. Ulceration was only identified in two of the 10 cases. For ulceration, kappa agreement score was 0.31 (fair).

CONCLUSION

This study supports the removal of mitotic count from staging, but shows that its scoring is substantially affected by interobserver variation, suggesting that more prescriptive guidelines might have a beneficial impact on its prognostic value.

Incorporation of dermoscopy improves inter-observer agreement among dermatopathologists in histologic assessment of melanocytic neoplasms

Histopathologic assessment of melanocytic neoplasms is the current gold standard of diagnosis. However, there are well recognized limitations including inter-observer diagnostic discordance. This study aimed to determine if integrating dermoscopy with histopathology of melanocytic neoplasms impacts diagnosis and improves inter-observer agreement. We conducted a prospective cohort study in a pigmented lesion clinic. Consecutive melanocytic lesions were identified for biopsy based on atypical gross or dermoscopic features. Standardized immunohistochemistry and levels were ordered on each specimen. The cases were randomized. Three dermatopathologists blinded to the clinical impression assessed each lesion. The cases were then re-randomized and re-assessed with addition of gross clinical and dermoscopic images. Inter-rater reliability (IRR) using Fleiss' kappa statistic revealed an increase from 0.447 without to 0.496 with dermoscopy amongst all dermatopathologists. The kappa increased from 0.495 before to 0.511 with dermoscopy in separating high-grade atypia or melanoma from moderate atypia or less. In 16 of 136 cases, at least 2 of 3 dermatopathologists favored a diagnosis of melanoma only after dermoscopy. In total, the consensus grade of atypia changed in 24.3% (33/ 136) of cases thereby representing changes to excisional margins and patient follow up. This study is limited by the cohort size. Dermoscopy significantly impacts diagnosis and improves identification of early melanomas in high risk populations and improves inter-observer agreement.

MicroRNA Ratios Distinguish Melanomas from Nevi

The use of microRNAs as biomarkers has been proposed for many diseases, including the diagnosis of melanoma. Although hundreds of microRNAs have been identified as differentially expressed in melanomas as compared to benign melanocytic lesions, a limited consensus has been achieved across studies, constraining the effective use of these potentially useful markers. In this study, we applied a machine learning-based pipeline to a dataset consisting of genetic features, clinical features, and next-generation microRNA sequencing from micro-dissected formalin-fixed paraffin embedded melanomas and their adjacent benign precursor nevi. We identified patient age and tumor cellularity as variables that frequently confound the measured expression of potentially diagnostic microRNAs. By employing the ratios of microRNAs that were either enriched or depleted in melanoma compared to the nevi as a normalization strategy, we developed a model that classified all the available published cohorts with an area under the receiver operating characteristic curve of 0.98. External validation on an independent cohort classified lesions with 81% sensitivity and 88% specificity and was uninfluenced by the tumor content of the sample or patient age.

Pathologists' agreement on treatment suggestions for melanocytic skin lesions

BACKGROUND

Although treatment guidelines exist for melanoma in situ and invasive melanoma, guidelines for other melanocytic skin lesions do not exist.

OBJECTIVE

To examine pathologists' treatment suggestions for a broad spectrum of melanocytic skin lesions and compare them with existing guidelines.

METHODS

Pathologists (N = 187) completed a survey and then provided diagnoses and treatment suggestions for 240 melanocytic skin lesions. Physician characteristics associated with treatment suggestions were evaluated with multivariable modeling.

RESULTS

Treatment suggestions were concordant with National Comprehensive Cancer Network guidelines for the majority of cases interpreted as melanoma in situ (73%) and invasive melanoma (86%). Greater variability of treatment suggestions was seen for other lesion types without existing treatment guidelines. Characteristics associated with provision of treatment suggestions discordant with National Comprehensive Cancer Network guidelines were low caseloads (invasive melanoma), lack of fellowship training or board certification (melanoma in situ), and more than 10 years of experience (invasive melanoma and melanoma in situ).

LIMITATIONS

Pathologists could not perform immunohistochemical staining or other diagnostic tests; only 1 glass side was provided per biopsy case.

CONCLUSIONS

Pathologists' treatment suggestions vary significantly for melanocytic lesions, with lower variability for lesion types with national guidelines. Results suggest the need for standardization of treatment guidelines for all melanocytic lesion types.

Pathological review of primary cutaneous malignant melanoma by a specialist skin cancer multidisciplinary team improves patient care in the UK

AIMS

The National Institute for Health and Care Excellence advocated the development of specialist skin cancer multidisciplinary teams (SSMDTs) for the management of higher risk invasive skin cancers in the UK. The interobserver variability in the histopathological assessment of primary cutaneous malignant melanoma (PCMM) is well recognised.

METHODS

We evaluated the discordance rates in the assessment of the histopathological criteria of PCMM based on the eighth American Joint Committee on Cancer (AJCC) melanoma staging system and subsequent change in prognosis and management following pathology review by an SSMDT.

RESULTS

353 cases of PCMM were referred to our SSMDT between April 2015 and May 2016. Cases in which there was a discrepancy in one or more histological parameters following expert review were collected retrospectively. Of 341 eligible cases, there were 94 (27.6%) in which there was an alteration in any parameter. There was interobserver agreement in final diagnosis in 96.8%, Breslow thickness in 86.8%, ulceration in 98.2%, microsatellites in 98.5%, tumour mitotic rate in 88.9%, histological subtype in 92.4%, growth phase in 98.5%, angiolymphatic invasion in 97.7%, perineural invasion in 98.8%, regression in 95.3% and tumour-infiltrating lymphocytes in 95.0%. A corresponding change in AJCC stage occurred in 23 cases (6.7%), with a resulting change in clinical management in 10 cases (2.9%).

CONCLUSIONS

Disagreements in the pathological assessment of PCMM can have significant clinical implications for a small number of patients. Our findings highlight the value of the SSMDT for high-quality care of patients with melanoma in the UK.

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.

Inter-observer variation in the histopathology reports of head and neck melanoma; a comparison between the seventh and eighth edition of the AJCC staging system

BACKGROUND

TNM staging of melanoma has recently been altered by the introduction of the 8th edition of the AJCC Cancer Staging manual. The purpose of this study is to analyze the inter-observer variation of histopathology reports and its effect on recommended treatment policy.

METHODS

We retrospectively analyzed 296 cases, diagnosed as primary cutaneous head and neck melanoma (2005-2016), referred to the Netherlands Cancer Institute (NCI) for treatment after prior diagnosis in another hospital (non-NCI). All reports were analyzed for patients demographics, tumor characteristics and histopathologic features.

RESULTS

In 53% and 40% of the cases, the histopathologic parameters were discordant, according to AJCC 7th and 8th edition, respectively. This indicated a perfect inter-observer agreement for the measurement of Breslow thickness (Intraclass correlation coefficient (ICC) = 0.981) and a substantial agreement for subtype (kappa statistic (κ) = 0.648) and ulceration (κ = 0.802), while only moderate for dermal mitotic activity (κ = 0.472). After NCI review, recommended treatment policies were changed in 13% and 11% of the patients when applying TNM 7 and TNM 8, respectively. Scheduling sentinel lymph node biopsy (SLNB) changed in 14 (5%) and 10 (3%) cases when using TNM 7 and TNM 8, respectively.

CONCLUSION

Review by a NCI pathologist of histopathologic parameters of primary cutaneous head and neck melanoma led to significant changes in treatment decision. Introduction of the AJCC 8th edition led to slightly less discordances between NCI and non-NCI reports and consequently smaller impact on treatment planning. Expert review remains indicated when a SLNB is considered for additional staging in selected cases.

Pathologists' diagnosis of invasive melanoma and melanocytic proliferations: observer accuracy and reproducibility study

Objective To quantify the accuracy and reproducibility of pathologists' diagnoses of melanocytic skin lesions.Design Observer accuracy and reproducibility study.Setting 10 US states.Participants Skin biopsy cases (n=240), grouped into sets of 36 or 48. Pathologists from 10 US states were randomized to independently interpret the same set on two occasions (phases 1 and 2), at least eight months apart.Main outcome measures Pathologists' interpretations were condensed into five classes: I (eg, nevus or mild atypia); II (eg, moderate atypia); III (eg, severe atypia or melanoma in situ); IV (eg, pathologic stage T1a (pT1a) early invasive melanoma); and V (eg, ≥pT1b invasive melanoma). Reproducibility was assessed by intraobserver and interobserver concordance rates, and accuracy by concordance with three reference diagnoses.Results In phase 1, 187 pathologists completed 8976 independent case interpretations resulting in an average of 10 (SD 4) different diagnostic terms applied to each case. Among pathologists interpreting the same cases in both phases, when pathologists diagnosed a case as class I or class V during phase 1, they gave the same diagnosis in phase 2 for the majority of cases (class I 76.7%; class V 82.6%). However, the intraobserver reproducibility was lower for cases interpreted as class II (35.2%), class III (59.5%), and class IV (63.2%). Average interobserver concordance rates were lower, but with similar trends. Accuracy using a consensus diagnosis of experienced pathologists as reference varied by class: I, 92% (95% confidence interval 90% to 94%); II, 25% (22% to 28%); III, 40% (37% to 44%); IV, 43% (39% to 46%); and V, 72% (69% to 75%). It is estimated that at a population level, 82.8% (81.0% to 84.5%) of melanocytic skin biopsy diagnoses would have their diagnosis verified if reviewed by a consensus reference panel of experienced pathologists, with 8.0% (6.2% to 9.9%) of cases overinterpreted by the initial pathologist and 9.2% (8.8% to 9.6%) underinterpreted.Conclusion Diagnoses spanning moderately dysplastic nevi to early stage invasive melanoma were neither reproducible nor accurate in this large study of pathologists in the USA. Efforts to improve clinical practice should include using a standardized classification system, acknowledging uncertainty in pathology reports, and developing tools such as molecular markers to support pathologists' visual assessments.

Automated quantification of proliferation with automated hot-spot selection in phosphohistone H3/MART1 dual-stained stage I/II melanoma

Background

Staging of melanoma includes quantification of a proliferation index, i.e., presumed melanocytic mitoses of H&E stains are counted manually in hot spots. Yet, its reproducibility and prognostic impact increases by immunohistochemical dual staining for phosphohistone H3 (PHH3) and MART1, which also may enable fully automated quantification by image analysis. To ensure manageable workloads and repeatable measurements in modern pathology, the study aimed to present an automated quantification of proliferation with automated hot-spot selection in PHH3/MART1-stained melanomas.

Methods

Formalin-fixed, paraffin-embedded tissue from 153 consecutive stage I/II melanoma patients was immunohistochemically dual-stained for PHH3 and MART1. Whole slide images were captured, and the number of PHH3/MART1-positive cells was manually and automatically counted in the global tumor area and in a manually and automatically selected hot spot, i.e., a fixed 1-mm² square. Bland-Altman plots and hypothesis tests compared manual and automated procedures, and the Cox proportional hazards model established their prognostic impact.

Results

The mean difference between manual and automated global counts was 2.9 cells/mm² (P = 0.0071) and 0.23 cells per hot spot (P = 0.96) for automated counts in manually and automatically selected hot spots. In 77 % of cases, manual and automated hot spots overlapped. Fully manual hot-spot counts yielded the highest prognostic performance with an adjusted hazard ratio of 5.5 (95 % CI, 1.3–24, P = 0.024) as opposed to 1.3 (95 % CI, 0.61–2.9, P = 0.47) for automated counts with automated hot spots.

Conclusions

The automated index and automated hot-spot selection were highly correlated to their manual counterpart, but altogether their prognostic impact was noticeably reduced. Because correct recognition of only one PHH3/MART1-positive cell seems important, extremely high sensitivity and specificity of the algorithm is required for prognostic purposes. Thus, automated analysis may still aid and improve the pathologists’ detection of mitoses in melanoma and possibly other malignancies.

Discordance of histopathologic parameters in cutaneous melanoma: Clinical implications

BACKGROUND

Histopathologic analysis remains the gold standard for the diagnosis of melanoma, however previous studies have shown a substantial rate of interobserver variability in the evaluation of melanocytic lesions.

OBJECTIVE

We sought to evaluate discordance in the histopathological diagnosis and microstaging parameters of melanoma and subsequent impact on clinical management.

METHODS

This was a retrospective review of 588 cases of cutaneous melanoma and melanoma in situ from January 2009 to December 2014 that were referred to Emory University Hospital, Atlanta, GA, for treatment. Per institutional policy, all outside melanoma biopsy specimens were reviewed internally. Outside and institutional reports were compared.

RESULTS

Disagreement between outside and internal reports resulted in a change in American Joint Committee on Cancer pathologic stage in 114/588 (19%) cases, resulting in a change in management based on National Comprehensive Cancer Network guidelines in 105/588 (18%) cases.

LIMITATIONS

Given the retrospective nature of data collection and the bias of a tertiary care referral center, cases in this study may not be representative of all melanoma diagnoses.

CONCLUSION

These findings confirm consistent subjectivity in the histopathologic interpretation of melanoma. This study emphasizes that a review of the primary biopsy specimen may lead to significant changes in tumor classification, resulting in meaningful changes in clinical management.

Prognostic factors in localized invasive primary cutaneous malignant melanoma: results of a large population-based study

BACKGROUND

The prognostic impact of several histopathological prognostic features in cutaneous malignant melanoma (CMM) remains controversial.

OBJECTIVES

To assess the independent prognostic value of mitotic rate, regression, tumour-infiltrating lymphocytes (TILs) and growth phase in primary stage I and II CMMs.

METHODS

Clinicohistopathological data were obtained from the Stockholm-Gotland registry for 4237 patients diagnosed with an incident primary stage I or II CMM followed up to December 2011. The risk of CMM-specific death was evaluated by a Cox regression model.

RESULTS

A mitotic rate of 1-10 mitoses per mm(2) [hazard ratio (HR) 1·69, 95% confidence interval (CI) 1·16-2·45] and > 10 mitoses per mm(2) (HR 2·27, 95% CI 1·46-3·52) were significant; TILs and regression were not. A more detailed analysis of data assessed between 1989 and 1995 confirmed significantly increased HRs for the presence vs. absence of mitoses (HR1-5/mm² 2·25, 95% CI 1·36-3·76; HR6-10/mm² 2·34, 95% CI 1·23-4·44; HR> 10/mm² 2·64, 95% CI 1·39-4·99). Other prognosticators were increasing T-stage vs. T1, presence of ulceration and presence of vertical growth phase (VGP). In T1 CMMs, an increasing tumour thickness vs. < 0·7 mm (HR0·7-0·8 mm 2·24, 95% CI 1·24-4·04; HR>0·8 mm  2·92, 95% CI 1·57-5·43) and presence of ulceration were significantly associated with higher HRs; mitotic rate, TILs, regression and growth phase were not.

CONCLUSIONS

Determinants of increased risk of CMM death in stage I and II CMMs were increasing T-stage, presence of ulceration, presence of mitoses and VGP. This was not found for TILs or regression.

Reproducibility of AJCC staging parameters in primary cutaneous melanoma: an analysis of 4,924 cases

BACKGROUND

Pathology reports are of critical importance for conveying information to clinicians who must make important management decisions for their patients. This study sought to assess and compare the precision, reproducibility, and completeness of external pathology reports and pathology reports generated by central review of each case in a large cohort of primary cutaneous melanoma patients.

METHODS

Details of matched external pathology reports and corresponding review reports for 4,924 primary cutaneous invasive melanomas diagnosed and treated at Melanoma Institute Australia (MIA) between 2001 and 2011 were analyzed.

RESULTS

Interobserver agreement was excellent for American Joint Committee on Cancer (AJCC) T staging parameters: Breslow thickness (intraclass correlation coefficient [ICC] 0.984), mitotic rate (ICC 0.833), and ulceration (kappa statistic [κ] 0.823). All three of these important pathologic variables were included in 92.4 and 66.9% of review (MIA) and external (non-MIA) pathology reports, respectively. Completeness of MIA and non-MIA pathology reports for the three essential T-staging criteria increased significantly from 87.9 to 94.6% (χ(2) = 9.1, df = 1, P = 0.003) and from 53.2 to 74.3% (χ(2) = 35.0, df = 1, P < 0.001) over the 10-year study period. The AJCC N staging parameter of microsatellites was recorded in only 43% of non-MIA reports and demonstrated moderate concordance (κ = 0.560).

CONCLUSIONS

Reproducibility and completeness of pathology reports for many important histopathologic features have improved in recent years. Nevertheless, the documentation of microsatellites remained poor in external pathology reports. To enhance the usefulness of the pathology report for the provision of optimal melanoma patient care, continued efforts to encourage pathologists to document its key features appear warranted.

The MPATH-Dx reporting schema for melanocytic proliferations and melanoma

BACKGROUND

The histologic diagnosis of melanoma and nevi can be subject to discordance and errors, potentially leading to inappropriate treatment and harm. Diagnostic terminology is not standardized, creating confusion for providers and patients and challenges for investigators.

OBJECTIVE

We sought to describe the development of a pathology reporting form for more precise research on melanoma and a diagnostic-treatment mapping tool for improved patient care and consistency in treatment.

METHODS

Three dermatopathologists independently reviewed melanocytic lesions randomly selected from a dermatopathology database. Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis (MPATH-Dx) reporting schema evolved from iterative case review and form revision.

RESULTS

Differences in diagnostic thresholds, interpretation, and nomenclature contributed to development of the MPATH-Dx histology reporting form, which groups lesions by similarities in histogenesis and degrees of atypia. Because preliminary results indicate greater agreement regarding suggested treatments than for specific diagnoses, the diverse terminologies of the MPATH-Dx histology reporting form were stratified by commonalities of treatments in the MPATH-Dx diagnostic-treatment mapping scheme.

LIMITATIONS

Without transformative advances in diagnostic paradigms, the interpretation of melanocytic lesions frequently remains subjective.

CONCLUSIONS

The MPATH-Dx diagnostic-treatment mapping scheme could diminish confusion for those receiving reports by categorizing diverse nomenclature into a hierarchy stratified by suggested management interventions.

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.

Pathologist interobserver variability of histologic features in childhood brain tumors: results from the CCG-945 study

In the Children's Cancer Group-945 trial, study design allowed estimation of overall interpathologist observational agreement for 6 histologic features frequently used in brain tumor diagnoses. We evaluated agreement between pairs of 5 experienced neuropathologists, who had knowledge of the general diagnoses prior to slide readings. We performed this study in an attempt to further improve pathologist interinstitutional agreement. The features mitosis, necrosis, and giant cells had "fair" overall kappa estimates of reproducibility of around 0.5, while endothelial proliferation had only a "poor" overall kappa of 0.35. The Rogot reproducibility index averaged 0.5 for pleomorphism and hyperchromia. The upper bounds for the 10 pair summary agreement estimates were at best 0.65 ("good") for all 6 features. These relatively low-reproducibility estimates for the very small number of histologic features being assessed in tumors institutionally diagnosed as high-grade gliomas indicate that neuropathologists either used different operational definitions or interpreted them differently. We found that we could rank the histologic features from best to worst agreement among study pathologists as necrosis, giant cells, mitosis, endothelial proliferation, hyperchromic nuclei, and pleomorphic cells. We suggest that neuropathologists involved in multi-institutional studies of putative therapies not discard these traditional histologic features, but rather develop standardized operational definitions and measure their variability before beginning the studies. Only after such histologic feature variability studies are conducted will we have the data to identify specific histologic features of value to clinicians and researchers. Agreement and strict adherence to improved nonsubjective diagnostic criteria would improve histologic feature reliability and, consequently, their usefulness in studies.

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.

Interobserver reproducibility of histological features in cutaneous malignant melanoma

AIMS

To assess the interobserver reproducibility of certain histological features proposed for the diagnosis of melanoma.

METHODS

In a series of melanomas, 13 histological parameters were analysed: dimension > 6 mm, asymmetry, poor circumscription, irregular confluent nests, single melanocytes predominating, absence of maturation, suprabasal melanocytes, asymmetrical melanin, melanin in deep cells, cytological atypia, mitoses, dermal lymphocytic infiltrate, and necrosis.

RESULTS

The agreement (reproducibility) between the nine observers was excellent (kappa > 0.75) for 10 of the 13 examined features (dimension > 6 mm, poor circumscription, irregular confluent nests, single melanocytes predominating, absence of maturation, suprabasal melanocytes, asymmetrical melanin, melanin in deep cells, mitoses, and necrosis). The agreement for asymmetry was very close to excellence (kappa = 0.74), and that for cytological atypia (kappa = 0.65) and dermal lymphocytic infiltrate (kappa = 0.47) was slightly lower, but in the fair to good agreement range. The kappa values obtained by comparison with the majority diagnosis were generally high (> or = 0.85); the mean value of kappa was lower (0.70) for only one parameter (dermal lymphocytic infiltrate).

CONCLUSIONS

The parameters investigated showed an overall good reproducibility.

Increasing incidence of lentigo maligna melanoma subtypes: northern California and national trends 1990-2000

Worldwide, lentigo maligna melanoma (LMM) comprises 4%-15% of cutaneous melanoma and occurs less commonly than superficial spreading or nodular subtypes. We assessed the incidence of melanoma subtypes in regional and national Surveillance, Epidemiology, and End Results (SEER) cancer registry data from 1990 to 2000. Because 30%-50% of SEER data were not classified by histogenetic type, we compared the observed SEER trends with an age-matched population of 1024 cases from Stanford University Medical Center (SUMC) (1995-2000). SEER data revealed lentigo maligna (LM) as the most prevalent in situ subtype (79%-83%), and that LMM has been increasing at a higher rate compared with other subtypes and to all invasive melanoma combined for patients aged 45-64 and > or =65 y. The SUMC data demonstrated LM and LMM as the only subtypes increasing in incidence over the study period. In both groups, LM comprised > or =75% of in situ melanoma and LMM > or =27% of invasive melanoma in men 65 y and older. Regional and national SEER data suggest an increasing incidence of LM and LMM, particularly in men > or =age 65. An increased incidence of LM subtypes should direct melanoma screening to heavily sun-exposed sites, where these subtypes predominate.

Histologic similarities between lentigo maligna and dysplastic nevus: importance of clinicopathologic distinction

BACKGROUND

Lentigo maligna (LM) can histologically simulate dysplastic nevus (DN). Partial biopsy of LM may lead to misdiagnosis.

METHODS

One hundred and fourteen cases of LM and LM melanoma (LMM) were diagnosed at the Veterans Affairs Palo Alto Health Care System (1993-2002). Biopsy and excision specimens for 68 in situ and 28 invasive melanomas were classified as having predominant classical LM features, predominant DN-like morphology, or a mixed pattern.

RESULTS

Biopsy specimens demonstrated a predominant classical pattern in 38% (25/65) LM and 36% (10/28) LMM, predominant DN-like features in 43% (28/65) LM and 25% (7/28) LMM, and mixed pattern in 15% (10/65) LM and 29% (8/28) LMM. Most LM and LMM biopsies were partial. Significant DN-like features were present in 51% LM and 57% LMM excision specimens. Median age was 72 years for LM and 73 years for LMM, mean lesion diameters were 1.3 and 1.7 cm for LM and LMM, respectively, and 85% of LM and 75% of LMM cases were located on heavily sun-exposed sites.

CONCLUSIONS

Misdiagnosis of LM or LMM as DN could have devastating results. Large pigmented lesions on sun-damaged skin in elderly individuals should warrant consideration of LM/LMM diagnosis, even in the setting of DN-like features histologically. Excisional biopsy may help to avoid misdiagnosis.

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.

Interobserver reproducibility of histopathologic prognostic variables in primary cutaneous melanomas

BACKGROUND

The prognosis for patients with localized primary cutaneous melanoma is known to depend principally on tumor thickness, and to a lesser extent on ulcerative state and Clark level. We have recently found in an analysis of 3661 patients that tumor mitotic rate (TMR) is also an important prognostic parameter, ranking second only to tumor thickness. However, few studies have assessed the accuracy and reproducibility with which these features of a melanoma are recorded by histopathologists.

AIM

To assess interobserver reproducibility of major pathologic prognostic parameters in cutaneous melanoma.

METHODS

Single hematoxylin and eosin-stained slides of 69 dermally invasive primary cutaneous melanomas were circulated among six pathologists with differing experience in the assessment of melanocytic tumors. The observers independently determined the tumor thickness, Clark level of invasion, ulcerative state, and TMR for each lesion. Intraclass correlation coefficients and kappa scores for multiple ratings per subject were calculated.

RESULTS

The intraclass correlation coefficients were 0.96 for tumor thickness and 0.76 for TMR. The kappa scores were 0.83 for ulcerative state and 0.60 for Clark level. These results indicated excellent agreement among the pathologists for measurements of tumor thickness, ulcerative state, and TMR and fair to good agreement for Clark level.

CONCLUSIONS

Appropriately trained and experienced histopathologists can assess prognostically important features of melanomas accurately and reproducibly. Given our recent finding of the significance of TMR in determining prognosis, it is important that this feature be assessed by a standardized method and documented for all primary cutaneous melanomas.

Interobserver reproducibility of ulceration assessment in primary cutaneous melanomas

In the recently revised melanoma staging system proposed by the American Joint Committee on Cancer (AJCC), ulceration assessment by the pathologist is a pivotal parameter. Patients upstaged because of ulceration might be included in adjuvant trials conducted in AJCC stage II melanoma patients. Therefore, accuracy based on interobserver reproducibility for melanoma ulceration assessment is crucial for proper clinical management. In some cases, it is extremely difficult, even for an experienced pathologist, to distinguish between trauma-induced ulceration, artifact and tumoral ulceration. Whether this difficulty may be resolved by the use of a more precise definition of ulceration has not been evaluated. Therefore, we have proposed a refined definition of melanoma ulceration and we tested whether this definition might improve the interobserver interpretative reproducibility of ulceration in primary cutaneous melanomas. The results of this study support the need for a more precise definition of melanoma ulceration that rules out biopsy trauma or processing artifact and could be incorporated into a standardised pathology worksheet for reporting primary melanomas.

Tumor mitotic rate is a more powerful prognostic indicator than ulceration in patients with primary cutaneous melanoma: an analysis of 3661 patients from a single center

BACKGROUND

The current study was performed to determine whether tumor mitotic rate (TMR) is a useful, independent prognostic factor in patients with localized cutaneous melanoma.

METHODS

From the Sydney Melanoma Unit database, 3661 patients with complete clinical information and details of primary tumor thickness, ulcerative state, and TMR were studied. TMR was expressed as mitoses per mm(2) in the dermal part of the tumor in which most mitoses were seen, as recommended in the 1982 revision of the 1972 Sydney classification of malignant melanoma. To determine which was the more prognostically useful method of grouping TMR, two separate methods (A and B) were used. Factors predicting melanoma-specific survival were analyzed using the Cox proportional hazards regression model.

RESULTS

Patients with a TMR of 0 mitoses/mm(2) had a significantly better survival than those with 1 mitosis/mm(2) (P < 0.0001) but no significant survival differences were recorded for the stepwise increases from 1-2, 2-3, 3-4, and 4-5/mm(2). Tumor thickness, ulceration, and TMR were closely correlated, whether TMR was grouped using Method A (0, 1-4, 5-10, and >/= 11 mitoses/mm(2)) or Method B (0-1, 2-4, and >/= 5 mitoses/mm(2)). However, Cox regression analysis indicated that the TMR was a highly significant independent prognostic factor, particularly when grouped according to Method A, in which it was second only to tumor thickness as the most powerful predictor of survival (P < 0.0001).

CONCLUSIONS

TMR is an important independent predictor of survival for melanoma patients. If confirmed by studies from other centers, it has the potential to further improve the accuracy of melanoma staging, as well as to define more rigidly the risk categories for patients entering clinical trials.

Clinical and histopathological features of malignant melanoma in germline CDKN2A mutation families

Primary cutaneous malignant melanomas (CMMs) from 26 individuals belonging to nine families with an identified mutation were clinically and histopathologically compared with 78 matched CMM controls and with a population-based series of CMMs ( = 667). All tumours were histopathologically re-examined. CDKN2A-associated cases were significantly less invasive compared with the matched controls, with an adjusted odds ratio (adjOR) of 2.9 and a 95% confidence interval (CI) of 1.0-8.1 ( = 0.04). According to the odds ratio (OR) values, CDKN2A-associated cases seemed to have tumours more often located on the head and neck (adjOR 2.9, 95% CI 0.6-13.7), with less inflammation (adjOR 0.7, 95% CI 0.3-1.8) and regression (adjOR 0.6, 95% CI 0.2-1.8) but more frequent histological ulceration (adjOR 1.9, 95% CI 0.6-5.8). In comparison with the population-based material, CDKN2A-associated cases were significantly younger at diagnosis (crude OR 3.5, 95% CI 1.6-7.5, divided at 50 years) and had less regressive reaction in their tumours (crude OR 0.35, 95% CI 0.2-0.8). No significant differences were seen for tumour thickness between the different groups. On multivariate analysis, the overall survival was significantly worse for thicker tumours and older age ( = 0.04 for both). To our knowledge this is the first description of the histopathological features of CMMs from families with mutations in the CDKN2A gene.

The revised American Joint Committee on Cancer staging system for melanoma

Substantial progress has been made in identifying the most significant clinical and pathologic characteristics of melanoma that predict for metastasis and survival. The American Joint Committee on Cancer (AJCC) staging system for cutaneous melanoma was recently revised to include these prognostic variables. Major changes in the staging include: (1) melanoma thickness and ulceration but not level of invasion will be used in the T category (except for T1 melanomas); (2) the number of metastatic lymph nodes rather than their gross dimensions and the delineation of clinically occult (ie, "microscopic") versus clinically apparent (ie, "macroscopic") nodal metastases will be used in the N category; (3) the site of distant metastases and the presence of elevated serum lactate dehydrogenase (LDH) will be used in the M category; (4) all patients with stage I, II, or III disease will be upstaged when a primary melanoma is ulcerated; (5) satellite metastases around a primary melanoma and in-transit metastases will be merged into a single staging entity that is grouped into stage III disease; and (6) distinct definitions for clinical and pathologic staging will take into account the new staging information gained from intraoperative lymphatic mapping and sentinel node biopsy.

Pathologic staging of melanoma

The American Joint Committee on Cancer (AJCC) recently launched a new staging system for cutaneous melanoma that was based on clinical experience with a large number of patients treated in major centers worldwide. As this system includes various histopathologic parameters of the primary melanoma and of melanoma metastasis, including micrometastases in the sentinel lymph node (SLN), they are discussed here. Special attention is given to ulceration of the primary tumor, because it remains a dominant prognostic parameter in addition to tumor thickness. Molecular markers that may reflect aggressive behavior of the primary melanoma also are described. Finally, pathologic examination of SLNs is addressed with emphasis on the efficacy of various microstaging approaches.

Inter-observer variation in the histopathological diagnosis of clinically suspicious pigmented skin lesions

When a biopsy is taken of a suspicious pigmented skin lesion, histological examination is expected to establish the definitive diagnosis. This study evaluated the inter-observer variation of 20 pathologists in the histological diagnosis of a randomly selected set of suspicious pigmented skin lesions (PSLs), by comparing their diagnoses to a reference diagnosis. Overall sensitivity for melanoma was 87%, ranging from 55% to 100% between the observers. Sensitivity was significantly lower for thin (Breslow thickness <1 mm) than for thick melanomas (83% versus 97%, p=0.005). Overall melanoma specificity was 94%, ranging from 83% to 100% between observers. Dysplastic naevus was the most important source of false-positive diagnoses, mainly in situ melanomas. Positive and negative predictive values in the given test set were 75% and 97%, respectively. In the case of melanoma, there was quite some variation in measured Breslow thickness. This would have led to a different therapeutic approach in 12% of the readings. Some of the variation seemed to be due to a different interpretation of the presence of a co-existent naevus. In 9% (3/35) of the readings, participants did not agree on the presence of ulceration. These results reflect a tendency to overdiagnose mainly thin melanomas in general histopathological practice. They also demonstrate variation in the assessment of major prognostic factors of melanoma.

Prognostic factors in invasive cutaneous malignant melanoma: a population-based study and review

A population-based study from Sweden identified 711 patients with cutaneous malignant melanoma diagnosed in 1965, 1975, 1985 and 1989. Prognostic factors were evaluated and a review of the literature was performed. On univariate analysis, thick tumours (> 0.8 mm) (odds ratio [OR] 1.8, 95% confidence interval [CI] 1.6-2.1), increasing Clark level (OR 1.8, 95% CI 1.6-2.0), ulceration (OR 1.8, 95% CI 1.6-2.0), nodular melanoma (OR 1.5, 95% CI 1.3-1.6) and increasing age (continuous variable, P < 0.0001) were associated with a shorter survival. Location on extremities (OR 0.8, 95% CI 0.7-0.9), inflammation (OR 0.8, 95% CI 0.7-0.9) and female gender (OR 0.8, 95% CI 0.8-0.9) were associated with improved survival. On multivariate analysis, thick tumours (> 0.8 mm) (OR 1.5, 95% CI 1.2-1.7) and ulceration (OR 1.4, 95% CI 1.2-1.6) were independently related to a poor prognosis, while location on extremities (OR 0.8, 95% CI 0.7-0.9), inflammation (OR 0.8, 95% CI 0.7-0.9) and female gender (OR 0.8, 95% CI 0.8-1.0) were associated with improved survival. No difference in mean tumour thickness was seen over time, but there was a significant increase in the percentage of thin melanomas (< 0.8 mm) in 1985 (P = 0.01) and 1989 (P = 0.002) compared with 1965. The incidence of melanomas with inflammation increased significantly (P = 0.04), as did age at diagnosis (P = 0.005).

Prognostic factors analysis of 17,600 melanoma patients: validation of the American Joint Committee on Cancer melanoma staging system

PURPOSE

The American Joint Committee on Cancer (AJCC) recently proposed major revisions of the tumor-node-metastases (TNM) categories and stage groupings for cutaneous melanoma. Thirteen cancer centers and cancer cooperative groups contributed staging and survival data from a total of 30,450 melanoma patients from their databases in order to validate this staging proposal.

PATIENTS AND METHODS

There were 17,600 melanoma patients with complete clinical, pathologic, and follow-up information. Factors predicting melanoma-specific survival rates were analyzed using the Cox proportional hazards regression model. Follow-up survival data for 5 years or longer were available for 73% of the patients.

RESULTS

This analysis demonstrated that (1) in the T category, tumor thickness and ulceration were the most powerful predictors of survival, and the level of invasion had a significant impact only within the subgroup of thin (< or = 1 mm) melanomas; (2) in the N category, the following three independent factors were identified: the number of metastatic nodes, whether nodal metastases were clinically occult or clinically apparent, and the presence or absence of primary tumor ulceration; and (3) in the M category, nonvisceral metastases was associated with a better survival compared with visceral metastases. A marked diversity in the natural history of pathologic stage III melanoma was demonstrated by five-fold differences in 5-year survival rates for defined subgroups. This analysis also demonstrated that large and complex data sets could be used effectively to examine prognosis and survival outcome in melanoma patients.

CONCLUSION

The results of this evidence-based methodology were incorporated into the AJCC melanoma staging as described in the companion publication.

Clinical and histologic features of level 2 cutaneous malignant melanoma associated with metastasis

BACKGROUND

Metastatic melanoma developing in patients with a level 2 primary cutaneous malignant melanoma (CMM) is rare but has been reported in studies with follow-up periods ranging up to 15 years. The objective of this study was to investigate level 2 CMM associated with metastasis in a population-based retrospective study.

METHODS

In this retrospective population-based study, all level 2 CMMs associated with metastases were identified in Western Australia during 1982-1989 and were followed up to the end of 1996.

RESULTS

Pathology reports of 2834 patients were examined. Of these, 1716 had a CMM of maximum tumor thickness 1 mm or less recorded on the pathology report. Of these, 67 had a metastatic melanoma reported on follow-up. Histologic review of these 67 cases under blind conditions identified 5 cases with a level 2 primary CMM followed by metastasis without another primary CMM. All these level 2 CMM showed established regression. Eight other patients were identified with a level 2 CMM, metastatic melanoma, and another primary CMM of at least level 3 invasion. These subsequent primaries occurred before the metastasis had been reported.

CONCLUSIONS

These findings suggest that metastasis from level 2 CMM without regression is very rare, if it occurs at all.

A new American Joint Committee on Cancer staging system for cutaneous melanoma

The Melanoma Staging Committee of the AJCC has proposed major revisions of the melanoma TNM and stage grouping criteria. The committee members represent most of the major cooperative groups and cancer centers worldwide with a special interest in melanoma; the committee also collectively has had clinical experience with over 40,000 patients. The new staging system better reflects independent prognostic factors that are used in clinical trials and in reporting the outcomes of various melanoma treatment modalities. Major revisions include 1) melanoma thickness and ulceration, but not level of invasion, to be used in the T classification; 2) the number of metastatic lymph nodes, rather than their gross dimensions, the delineation of microscopic versus macroscopic lymph node metastases, and presence of ulceration of the primary melanoma to be used in the N classification; 3) the site of distant metastases and the presence of elevated serum LDH, to be used in the M classification; 4) an upstaging of all patients with Stage I,II, and III disease when a primary melanoma is ulcerated; 5) a merging of satellite metastases around a primary melanoma and in-transit metastases into a single staging entity that is grouped into Stage III disease; and 6) a new convention for defining clinical and pathologic staging so as to take into account the new staging information gained from intraoperative lymphatic mapping and sentinel lymph node biopsy. The AJC Melanoma Staging Committee invites comments and suggestions regarding this proposed staging system before a final recommendation is made.

Pathologic parameters in the diagnosis and prognosis of primary cutaneous melanoma

Significant progress has been made in the last 10 years on the identification of histologic parameters that are independent predictors of melanoma prognosis, immunohistochemical markers of cells of melanocytic origin and changes in adhesion molecules, cytoskeletal proteins, growth factor receptors, cell signaling, and nuclear proliferation proteins associated with tumor progression. Histologic criteria may never be completely sufficient to predict behavior accurately, because the fundamental change that renders a cell aggressive may not be morphologically reflected and may require immunohistochemical or other molecular markers to establish behavior. To date, it is humbling that no immunohistochemical or molecular marker provides a greater predictable value for aggressive behavior than does the simple calibrated ocular micrometer to measure tumor thickness. Nevertheless, development of multiple histologic parameters with the concept of nontumorigenic RGP and tumorigenic VGP provides a reliable statistical model to predict metastases. Fortunately, nontumorigenic RGP melanomas with greater than 75% regression are rare. Thus, individual patients with melanoma without regression and without the tumorigenic VGP can be given reasonable assurance of 100% survival. Nevertheless, this assurance is based on a statistical model with a finite population studied. Additional studies are needed to confirm this model, as well as more definitive markers to precisely predict outcome for those individuals with tumorigenic VGP melanoma.

Malignant melanoma in patients treated for psoriasis with methoxsalen (psoralen) and ultraviolet A radiation (PUVA). The PUVA Follow-Up Study

BACKGROUND

Photochemotherapy with oral methoxsalen (psoralen) and ultraviolet A radiation (PUVA) is an effective treatment for psoriasis. However, PUVA is mutagenic, increases the risk of squamous-cell skin cancer, and can cause irregular, pigmented skin lesions. We studied the occurrence of melanoma among patients treated with PUVA.

METHODS

We prospectively identified cases of melanoma and documented the extent of exposure to PUVA among 1380 patients with psoriasis who were first treated with PUVA in 1975 or 1976. Using incidence data, we calculated the expected incidence of melanoma in this cohort and compared it with the observed incidence. Using regression models, we assessed the risks of melanoma associated with a long time (> or = 15 years) since the first treatment and with a large number of PUVA treatments (> or = 250).

RESULTS

From 1975 through 1990, we detected four malignant melanomas, about the number expected in the overall population (relative risk, 1.1). From 1991 through 1996, we detected seven malignant melanomas (relative risk, 5.4; 95 percent confidence interval, 2.2 to 11.1). The risk of melanoma was higher in the later period than in the earlier one (incidence-rate ratio, 3.8) and higher among patients who received at least 250 PUVA treatments than among those who received fewer treatments (incidence-rate ratio, 3.1).

CONCLUSIONS

About 15 years after the first treatment with PUVA, the risk of malignant melanoma increases, especially among patients who receive 250 treatments or more.

A nationwide survey of observer variation in the diagnosis of thin cutaneous malignant melanoma including the MIN terminology. CRC Melanoma Pathology Panel

AIM

To investigate observer variation in the diagnosis of thin cutaneous malignant melanoma and related lesions in a nationwide sample of histopathologists in the UK.

METHODS

Out of a random sample of 195 pathologists, 148 (76%) participated in two circulations, the first with 20 slides and the second with 25 slides. The results were compared with those for the Cancer Research Campaign (CRC) Melanoma Pathology Panel, consisting of seven histopathologists and one dermatopathologist, which had developed and evaluated diagnostic criteria.

RESULTS

In the first circulation, when no standardised diagnostic criteria were used, a fair level of agreement was achieved for an overall diagnosis using the categories benign naevi with no atypia, benign naevi with atypia and melanoma (Kappa = 0.45). This was low compared with the agreement of the panel who used agreed criteria (Kappa = 0.75). Moreover, participants in the nationwide survey were more likely to diagnose melanoma and less likely to diagnose benign naevi without atypia than the panel. In the second circulation, when diagnostic criteria and diagrams were used, there was a higher level of agreement for overall diagnosis using the categories benign, melanocytic intraepidermal neoplasia (MIN) with or without microinvasion and melanoma with vertical growth phase, and was the same as that achieved by the panel using the same criteria (Kappa = 0.68).

CONCLUSIONS

As the incidence rate of thin melanomas has been increasing in the UK, it is important that standardised diagnostic criteria are used to ensure accurate reporting of incidence and correct management of patients. The use of MIN and the vertical growth phase seemed to be generally acceptable.

Discordance in the histopathologic diagnosis of melanoma and melanocytic nevi between expert pathologists

The reliability of a diagnostic test depends on the reproducibility of the result. Many clinical diagnostic tests can be quantified with established ranges and standard deviations. Other tests are more subjective, such as those that depend on analysis of a visual image with an increased possibility of variance in the result. To study this variance, the authors analyzed the performance of expert pathologists in the interpretation of cutaneous melanocytic tumors. A panel of expert pathologists was convened to review anatomic pathology specimens from melanocytic tumors. Each pathologist submitted five specimens, from which 37 were selected for review. Only one slide was used for each case. All specimens were interpreted by each pathologist without consultation with each other. In addition to standard diagnostic terms, each specimen was designated as benign, malignant, or indeterminate. Statistical analysis was used to determine the degree of concordance. The combined kappa statistic for the eight observers and three possible outcomes (benign, malignant, or indeterminate) was 0.50. A kappa statistic of this magnitude, is defined as being moderate. In 62% of the specimens, there was unanimous agreement or only one discordant designation. Thirty-eight percent had two or more discordant interpretations. No single pathologist had a disproportionate number of discordant designations. This study mimics the consultation practice of anatomic pathology and shows the variability and discordance in diagnostic language and designation of biological behavior. The results suggest the criteria for the diagnosis of melanomas and melanocytic nevi need to be refined and more consistently applied.

Observer variation in histological classification of cutaneous malignant melanoma

To evaluate the variations within and between observers in the interpretation of important histological prognostic factors, a series of 96 melanoma patients was randomly selected from a database of 1691 patients with cutaneous malignant melanoma. The stained sections were examined on two occasions by four experienced pathologists. Analysis by observed agreement and kappa statistics showed maximal tumour thickness to be the best reproducible variable, with ulceration the second best. Regression was the least reproducible, with level of invasion and type of melanoma in the mid range. Intra-observer variation was uniformly less than inter-observer variation for each variable. For tumour thickness a variance component analysis was done to quantify the variability further. The clinician should not base his choice of treatment entirely on the microscopic classification but take into consideration the clinical course and appearance of the tumour.