Revision of the Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis Classification Schema for Melanocytic Lesions: A Consensus Statement.

Importance: A standardized pathology classification system for melanocytic lesions is needed to aid both pathologists and clinicians in cataloging currently existing diverse terminologies and in the diagnosis and treatment of patients. The Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis (MPATH-Dx) has been developed for this purpose. Objective: To revise the MPATH-Dx version 1.0 classification tool, using feedback from dermatopathologists participating in the National Institutes of Health-funded Reducing Errors in Melanocytic Interpretations (REMI) Study and from members of the International Melanoma Pathology Study Group (IMPSG). Evidence Review: Practicing dermatopathologists recruited from 40 US states participated in the 2-year REMI study and provided feedback on the MPATH-Dx version 1.0 tool. Independently, member dermatopathologists participating in an IMPSG workshop dedicated to the MPATH-Dx schema provided additional input for refining the MPATH-Dx tool. A reference panel of 3 dermatopathologists, the original authors of the MPATH-Dx version 1.0 tool, integrated all feedback into an updated and refined MPATH-Dx version 2.0. Findings: The new MPATH-Dx version 2.0 schema simplifies the original 5-class hierarchy into 4 classes to improve diagnostic concordance and to provide more explicit guidance in the treatment of patients. This new version also has clearly defined histopathological criteria for classification of classes I and II lesions; has specific provisions for the most frequently encountered low-cumulative sun damage pathway of melanoma progression, as well as other, less common World Health Organization pathways to melanoma; provides guidance for classifying intermediate class II tumors vs melanoma; and recognizes a subset of pT1a melanomas with very low risk and possible eventual reclassification as neoplasms lacking criteria for melanoma. Conclusions and Relevance: The implementation of the newly revised MPATH-Dx version 2.0 schema into clinical practice is anticipated to provide a robust tool and adjunct for standardized diagnostic reporting of melanocytic lesions and management of patients to the benefit of both health care practitioners and patients.

Sentinel lymph node melanoma metastases: Assessment of tumor burden for clinical prediction of outcome in the first Multicenter Selective Lymphadenectomy Trial (MSLT-I).

PURPOSE: As clinical management decisions in patients with Stage III melanoma have become more complex, precise pathologic characterization of sentinel lymph node (SLN) metastases has become critical to guide management. The extent of SLN involvement correlates with risk of adverse outcomes, but reported methods of disease quantification vary. We examined SLN metastases from patients participating in an international clinical trial and compared several methods of tumor burden quantification. METHODS: SLNs from 146 node-positive patients in the first Multicenter Selective Lymphadenectomy Trial (MSLT-I) were centrally-reviewed and characterized by number of tumor-positive nodes, percent nodal area tumor replacement, maximum dimension of largest metastasis, tumor penetrative depth, number of tumor foci, metastasis microanatomic location, and extracapsular extension. These data were analyzed for correlation with non-SLN metastasis and melanoma-specific survival (MSS). RESULTS: The median number of tumor-involved SLNs was 1. The median maximum metastasis dimension was 1.11 mm. Median SLN area involvement was 1.5%. Tumor burden measures were highly correlated with each other. Factors associated with non-SLN metastasis by univariable analysis were primary tumor ulceration and extent of metastases. Tumor thickness, ulceration, non-SLN metastasis and multiple measures of SLN tumor burden were significantly related to MSS on univariable analysis. After multivariable adjustment, number of involved SLNs (p = 0.05) and percent nodal area tumor replacement (p = 0.02) were independent predictors of MSS. CONCLUSION: Central review of MSLT-I pathology indicates that primary tumor and SLN tumor characteristics predict non-SLN metastasis and MSS. Percent nodal involvement was more powerfully prognostic than the more commonly used maximum dimension of largest metastasis.

Preoperative Ultrasound Assessment of Regional Lymph Nodes in Melanoma Patients Does not Provide Reliable Nodal Staging: Results From a Large Multicenter Trial.

OBJECTIVE: To assess whether preoperative ultrasound (US) assessment of regional lymph nodes in patients who present with primary cutaneous melanoma provides accurate staging. BACKGROUND: It has been suggested that preoperative US could avoid the need for sentinel node (SN) biopsy, but in most single-institution reports, the sensitivity of preoperative US has been low. METHODS: Preoperative US data and SNB results were analyzed for patients enrolled at 20 centers participating in the screening phase of the second Multicenter Selective Lymphadenectomy Trial. Excised SNs were histopathologically assessed and considered positive if any melanoma was seen. RESULTS: SNs were identified and removed from 2859 patients who had preoperative US evaluation. Among those patients, 548 had SN metastases. US was positive (abnormal) in 87 patients (3.0%). Among SN-positive patients, 39 (7.1%) had an abnormal US. When analyzed by lymph node basin, 3302 basins were evaluated, and 38 were true positive (1.2%). By basin, the sensitivity of US was 6.6% (95% confidence interval: 4.6-8.7) and the specificity 98.0% (95% CI: 97.5-98.5). Median cross-sectional area of all SN metastases was 0.13 mm2; in US true-positive nodes, it was 6.8 mm2. US sensitivity increased with increasing Breslow thickness of the primary melanoma (0% for ≤1 mm thickness, 11.9% for >4 mm thickness). US sensitivity was not significantly greater with higher trial center volume or with pre-US lymphoscintigraphy. CONCLUSION: In the MSLT-II screening phase population, SN tumor volume was usually too small to be reliably detected by US. For accurate nodal staging to guide the management of melanoma patients, US is not an effective substitute for SN biopsy.

Histomorphologic assessment and interobserver diagnostic reproducibility of atypical spitzoid melanocytic neoplasms with long-term follow-up.

Predicting clinical behavior of atypical Spitz tumors remains problematic. In this study, we assessed interobserver agreement of diagnosis by 13 expert dermatopathologists for atypical Spitz tumors (n=75). We determined which histomorphologic features were most heavily weighted for their diagnostic significance by the experts and also which histomorphologic features had a statistically significant correlation with clinical outcome. There was a low interobserver agreement among the experts in categorizing lesions as malignant versus nonmalignant (κ=0.30). The histomorphologic features that were given the most diagnostic significance by the experts were: consumption of the epidermis, atypical mitoses, high-grade cytologic atypia, and mitotic rate. Conversely, the histomorphologic features that most correlated with disease progression were: frequent mitoses, deep mitoses, asymmetry, high-grade cytologic atypia, and ulceration. The presence and/or pattern of pagetoid spread, consumption of the epidermis, and lymphoid aggregates demonstrated no association with clinical behavior. The results support the assertion that there is a lack of consensus in the assessment of atypical Spitz tumors by expert dermatopathologists. Importantly, many features used to distinguish conventional melanoma from nevi were not useful in predicting the behavior of atypical Spitz tumors. This study may provide some guidance regarding histologic assessment of these enigmatic tumors.

Optimized assessment of sentinel lymph nodes for metastatic melanoma: implications for regional surgery and overall treatment planning.

Correct identification of the sentinel node (SN) and accurate evaluation of this node's tumor status constitute the most precise technique for staging clinically localized cutaneous melanoma. However, even if tumor is present in the SN (as in approximately 20% of patients), the remaining nodes in the basin are often tumor-free. We have found that the Breslow thickness of the primary, the relative area of tumor in the SN (with respect to the area of the SN), and the density of dendritic leukocytes in the SN paracortex not only can predict the likelihood of nonsentinel node metastases but also are correlated with likelihood of tumor recurrence and melanoma-specific survival. The most robust of these predictors is relative tumor area, and this may be used as the basis of practical predictive algorithms.