Estimating Mastectomy Weight From Standard Breast Measurements, BMI, and Sister Bra Size: A Simple Clinical Formula

Accurately estimating breast weight is essential for surgical planning, particularly in mastectomy and immediate reconstruction. Current prediction methods are often impractical in routine clinical settings because of cost, complexity, or accessibility.

The authors sought to derive and validate a simple formula that can be utilized by both patients and providers to estimate mastectomy specimen weight using standard breast measurements, BMI, and sister bra size (SS).

The authors performed a retrospective review of 177 mastectomy patients (333 breasts) from University of California, Los Angeles. Data collected included nipple-to-inframammary fold (N-IMF) distance, sternal notch-to-nipple (SN-N) distance, BMI, Regnault ptosis grade, and SS. Spearman and Pearson correlation tests were conducted to identify terms with strong predictive strength. A formula with 3 strong predictive terms was derived using linear regression.

The 3 terms included in the predictive equation were BMI × N-IMF (ρ = 0.857; P < .001), SS × N-IMF (ρ = 0.832; P < .001), and SN-N² (ρ = 0.72; P < .001). The final formula, which was Mastectomy specimen weight (g) = 1.32 × (BMI × N-IMF) + 2.0 × (SS × N-IMF) + 0.13 × (SN-N)² - 32 demonstrated strong predictive performance (R ² = 0.783; root mean square error = ±119 g).

The authors present a simple formula that can accurately estimate mastectomy specimen weight using BMI, N-IMF distance, SN-N distance, and SS.

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