EP206: The Art and Science of Diagnosing: Dr. Raymond Barnhill on Melanocytic Lesions

Dr. Raymond Barnhill on Diagnostic Drift, Uncertainty, and the MPATH-Dx V2.0 Approach to Melanocytic Lesions

In this episode of The Girl Doc Survival Guide, Christine interviews Dr. Raymond Barnhill, a world-recognized dermatopathology expert known for work on diagnostically challenging melanocytic lesions, melanoma pathology references, and contributions to WHO skin tumor classification and AJCC melanoma staging. Dr. Barnhill shares career anecdotes and key communities at Yale and in Boston, collaborations with numerous melanoma leaders, and the founding of the North American Melanoma Pathology Study Group and the International Melanoma Pathology Study Group, as well as participation in the NIH-funded MPATH Study Group. The discussion focuses on overdiagnosis, underdiagnosis, and diagnostic discordance in melanocytic lesions, including evidence of diagnostic drift toward calling more lesions melanoma over time and the overlap between melanoma criteria and atypical/dysplastic nevi. He describes MPATH research, explains the revised MPATH-Dx V2.0 schema, explicitly recognizing uncertainty along a continuum rather than a strict benign/malignant threshold. He emphasizes practical diagnostic approaches including measuring lesion size (noting a 4 mm threshold associated with conventional dysplastic nevi and increasing concern at larger sizes), focusing on key architectural features (junctional nest variation/disarray and lentiginous proliferation), using nuclear size relative to keratinocyte nuclei (including a 1.5× threshold and counting atypical cells per high-power field) while accounting for site-specific pitfalls such as scalp nevi. The conversation also covers “gestalt” versus systematic review, the importance of due diligence using full clinical and morphologic information before ancillary testing, and cautions against overreliance on immunohistochemistry or molecular tests. Dr. Barnhill closes with career advice ends with a message that setbacks can be opportunities for growth.

00:00 Welcome + Meet Dr. Raymond Barnhill (Dermatopathology Legend)

01:51 Career Origins & Melanoma Pathology Mentors (Yale → Boston)

03:59 Building Melanoma Pathology Study Groups (North American & International)

05:57 Overdiagnosis, Diagnostic Drift & Why Discordance Happens

09:43 Inside the MPATH Study: Measuring Interobserver & Intraobserver Agreement

11:39 MPATH-Dx V2.0 Explained: Standardized Classes & Treatment Guidance

13:59 Redefining “Low-Risk” Melanoma: Stringent pT1a Criteria + Embracing Uncertainty

18:47 Practical Grading Tips: Lesion Size, Architecture & Nuclear Atypia Thresholds

22:42 Gestalt vs Due Diligence: Avoiding Traps + Using IHC/Molecular Wisely (PRAME)

28:39 Career Advice: Passion, Mentors, Community + Final Reflections