Background: T1 melanoma staging is significantly affected by tissue sampling approaches, which have not been well characterized.
Objective: We sought to characterize presence of mitotic figures across a minimum of 5 sequential sections of T1 melanomas.
Methods: A cohort of T1 melanomas with either 5 (single section per slide) or 10 (2 sections per slide) sequential sections (5-μm thickness) per case were prepared and examined for mitotic figures.
Results: In all, 44 of 82 T1 melanomas (54%) were classified as T1b. The number of sections with a mitotic figure present ranged from only 1 of 5 sections (n = 5 of 44 cases, 11.4%) to all 5 (n = 20 of 44 cases, 45.5%). A sequential approach versus a nonsequential approach did not appear to matter.
Limitation: Cases were taken from a single pathology practice in the Pacific Northwest, which may not generalize to other populations in the United States.
Conclusion: The variation in the presence of mitotic figures within sequential sections supports reviewing 3 to 5 sections to fulfill American Joint Committee on Cancer recommendations. The prognostic significance of a T1b melanoma with a rare mitotic figure on a single section versus a T1b melanoma with mitotic figures on multiple sections deserves more attention to see if further subclassification is possible or even necessary.
Keywords: American Joint Committee on Cancer TNM staging; T1b; accuracy; mitosis; mitotic rate; reproducibility; variability.
Copyright © 2014 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.