THE EVALUATION OF DIAGNOSTIC AND PROGNOSTIC CRITERIA AND THE TERMINOLOGY OF THIN CUTANEOUS MALIGNANT-MELANOMA BY THE CRC MELANOMA PATHOLOGYPANEL

Sections from 95 skin lesions excised at pigmented lesion clinics in E ngland and Scotland were studied by eight histopathologists in order t o evaluate consistency in the use of histopathological terms for featu res of diagnostic and prognostic importance for cutaneous malignant me lanoma, The level of agreement (kappa) amongst the panel improved afte r discussion and re-definement of criteria for several features, These included, architectural and nuclear atypia, pagetoid infiltration and radial and vertical growth phases. A high level of agreement was achi eved for an overall benign or malignant diagnosis (kappa = 0.77) but u se of more specific terms such as benign naevi with atypia and melanom a less than or equal to 0.76 mm thickness, was associated with only an intermediate level of agreement, Of the original diagnosis of melanom a, 17% were re-classified by the panel as benign with atypia and 2% re ported to be benign were judged to be melanoma, This reflected the hig h proportion of borderline lesions in the study, The use of standardiz ed diagnostic criteria with precise definitions has been shown to impr ove consistency in diagnosis and it is recommended for general applica tion, From this should emanate more reliable incidence figures for thi n melanoma, and improved understanding of the nature of these early le sions, to the benefit of patient and clinician alike, The poor concord ance in distinguishing severe dysplasia in the junctional component of melanocyte proliferations from melanoma in situ and superficial derma l invasion improved only modestly despite intensive efforts, Since mel anoma in situ and severe dysplasia cannot be distinguished by objectiv e measurements and since their clinical management is the same, the pa nel suggests that attempts to separate them in diagnostic reports shou ld be discontinued and they could both be referred to as melanocytic i ntraepidermal neoplasia (MIN), If it becomes accepted that dermal inva sion without a vertical growth component can also be managed identical ly to MIN, then this invasive radial phase may be appropriately referr ed to as microinvasion and linked to MIN for the purposes of clinical management.