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Observational Study Examining the Diagnostic Practice of Ki67 Staining for Melanocytic Lesions

Vyas, Nikki S. MD*; Charifa, Ahmad MD; Desman, Garrett T. MD*; Goldberg, Matthew MD*; Singh, Rajendra MD*; Phelps, Robert G. MD*; McNiff, Jennifer M. MD

The American Journal of Dermatopathology: July 2019 - Volume 41 - Issue 7 - p 488–491
doi: 10.1097/DAD.0000000000001379
Original Study
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Background: Dermatopathologists routinely use Ki67 immunostaining to assess atypical melanocytic lesions with a dermal component to determine whether an ambiguous tumor is melanoma. However, there is no universal standard of use for Ki67 in melanocytic neoplasms. We sought to observe the real-world use of Ki67 in the diagnosis of melanocytic lesions and establish a best practice recommendation.

Methods: We searched dermatopathology reports from 2 academic practices for melanocytic lesions in which Ki67 staining was used for diagnosis. The proliferation rate was compared between cases diagnosed as benign (not requiring re-excision), moderate to severely dysplastic or atypical Spitz nevi (requiring re-excision), and malignant melanoma. The use of other melanocytic markers and consensus review was also recorded and compared between institutions.

Results: Pathology reports for 106 cases were reviewed. A high Ki67 proliferation rate (n = 18) favored a diagnosis of melanoma or nevi requiring re-excision (15/18, 83.3%) versus a benign nevus (3/18, 16.67%). A high Ki67 rate was 71.4%–90.9% sensitive and 40%–56% specific for the diagnosis of nevus requiring re-excision or melanoma. Institutional practices differed in regard to reporting of Ki67 staining, the use of multiple markers in the workup of atypical melanocytic lesions (HMB45, Melan-A, Ki67 being most common), and consensus review.

Conclusions: A negative or low Ki67 proliferation rate correlates well with rendering of a benign diagnosis. However, a low proliferation rate does not preclude the diagnosis of melanoma. Ki67 staining is most commonly used as an ancillary test to support a diagnosis after other factors have been considered, such as histopathologic morphology and results of additional concurrently used stains.

*Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY; and

Department of Dermatology, Yale University School of Medicine, New Haven, CT.

Correspondence: Nikki S. Vyas, MD, Icahn School of Medicine at Mount Sinai, Department of Pathology, 1468 Madison Avenue, Box 1194, New York, NY 10029 (e-mail: nikki.vyas@mountsinai.org).

The authors declare no conflicts of interest.

Dr Vyas received a 2017 Mentorship Award from the American Society of Dermatopathology (ASDP) for work on this project.

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