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

Changing pigmentation in a solitary scalp lesion

A healthy 66 year-old man presented with a complaint of changes within a nodule on the scalp, which had first appeared over 10 years prior. He had no previous history of skin cancer.  On physical examination a solitary, asymmetric, purple-black nodule with irregular borders was identified on the right vertex of his scalp. The remainder of his examination did not reveal any additional lesions

Changing pigmentation in a solitary scalp lesion

A healthy 66 year-old man presented with a complaint of changes within a nodule on the scalp, which had first appeared over 10 years prior. He had no previous history of skin cancer.  On physical examination a solitary, asymmetric, purple-black nodule with irregular borders was identified on the right vertex of his scalp. The remainder of his examination did not reveal any additional lesions

Microcystic adnexal carcinoma arising within a nevus sebaceus.

Nevus sebaceus (NS) is a congenital skin lesion arising on the face and scalp that has been linked to the development of various carcinomas. We describe a case of microcystic adnexal carcinoma (MAC) arising in an NS on the scalp of a 62-year-old man. Excisional skin biopsy and hematoxylin and eosin stains were performed to examine the specimen. Serial sections revealed papillomatosis typical of NS, with focal changes consistent with syringocystadenoma papilliferum. Adjacent to the syringocystadenoma papilliferum was an area containing small epithelial islands that extended focally into the subcutaneous layer. The cystic islands were embedded in a desmoplastic stroma with poor circumscription, consistent with MAC. This case presents a rare finding of MAC within an NS