An external validation of a novel predictive algorithm for male nipple areolar positioning: an improvement to current practice through a multicenter endeavor

Floyd W. Timmermans, Laure Ruyssinck, Sterre E. Mokken, Marlon Buncamper, Kevin M. Veen, Margriet G. Mullender, Karel E.Y. Claes, Mark Bram Bouman, Stanislas Monstrey, Timotheus C. van de Grift

Research output: Contribution to journalArticleAcademicpeer-review


The correct positioning of nipple-areolar complexes (NAC) during gender-affirming mastectomies remains a particular challenge. Recently, a Dutch two-step algorithm was proposed predicting the most ideal NAC-position derived from a large cisgender male cohort. We aimed to externally validate this algorithm in a Belgian cohort. The Belgian validation cohort consisted of cisgender men. Based on patient-specific anthropometry, the algorithm predicts nipple-nipple distance (NN) and sternal-notch-to-nipple distance (SNN). Predictions were externally validated using the performance measures: R 2-value, means squared error (MSE) and mean absolute percentage error (MAPE). Additionally, data were collected from a Belgian and Dutch cohort of transgender men having undergone mastectomy with free nipple grafts. The observed and predicted NN and SNN were compared and the inter-center variability was assessed. A total of 51 Belgian cisgender and 25 transgender men were included, as well as 150 Dutch cisgender and 96 transgender men. Respectively, the performance measures (R 2-value, MSE and MAPE) for NN were 0.315, 2.35 (95%CI:0–6.9), 4.9% (95%CI:3.8–6.1) and 0.423, 1.51 (95%CI:0–4.02), 4.73%(95%CI:3.7–5.7) for SNN. When applying the algorithm to both transgender cohorts, the predicted SNN was larger in both Dutch (17.1measured(±1.7) vs. 18.7predicted(±1.4), p= <0.001) and Belgian (16.2measured(±1.8) vs. 18.4predicted(±1.5), p= <0.001) cohorts, whereas NN was too long in the Belgian (22.0measured(±2.6) vs. 21.2predicted(±1.6), p = 0.025) and too short in the Dutch cohort (19.8measured(±1.8) vs. 20.7predicted(±1.9), p = 0.001). Both models performed well in external validation. This indicates that this two-step algorithm provides a reproducible and accurate clinical tool in determining the most ideal patient-tailored NAC-position in transgender men seeking gender-affirming chest surgery.

Original languageEnglish
Pages (from-to)103-108
Number of pages6
Issue number1-6
Early online date7 Nov 2021
Publication statusPublished - 2023


  • Mastectomy
  • anthropometry
  • gender surgery
  • morphology
  • nipple reconstruction
  • transgender individual

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