Date of Award

January 2024

Document Type


Degree Name

Medical Doctor (MD)



First Advisor

Elizabeth Berger

Second Advisor

Rachel Greenup


Axillary staging in early-staged breast cancer can impact adjuvant treatment options but is also associated with increased morbidity. The incidence of pathologic nodal positivity in patients with microinvasive or T1a disease by histologic subtype is not well characterized and thus, the value of sentinel node biopsy remains controversial in these patients. We sought to analyze patient demographics and tumor characteristics associated with pathologic nodal disease in patients with clinically node negative (cN0), microinvasive and T1a breast cancers.Women >18 years old with clinically node negative (cN0) and pathologic microinvasive or T1a breast cancer who underwent upfront surgery were identified from the National Cancer Database (2004 – 2019). Pathologic nodal stage at time of surgery was the primary outcome of interest. Multivariable logistic modeling was used to assess predictors of pathologic nodal positivity (pN+) in patients with either microinvasive or T1a tumor based on clinicopathologic factors. Overall, N= 141,840 women were included in the final analytic cohort; 139,206 (98.1%) had pN0 disease and 2,634 (1.9%) had pN+ disease. Rates of pN+ disease differed by race and ethnicity with 1.64% of Asian women, 2.84% of Black women, 2.17% of Latina women, 3.14% of Native American women, and 1.72% of White women were node positive (p<0.01). Age was also predictive of pN+ disease; 2.75% of patients <50 years old were node positive compared to 1.69% of pts 50-70 years old, and 1.50% of pts >70 years old (p<0.01). Receptor status was also predictive of pN+ disease [2.30% Hormone Receptor positive (HR+)/Human Epidermal Growth Factor Receptor 2 negative (HER2-), 1.84% triple positive, 2.66% triple negative breast cancer (TNBC), and 4.21% HR-/HER2+, p<0.01], as was histology [2.12% ductal vs 2.59% lobular, p<0.01]. Multivariable analysis demonstrated that compared to White women, Black women [adjusted odds ratio (AOR) 1.54 (95% CI 1.36-1.74)] had higher odds of pN+ disease, but there was no statistically significant difference for Asian, Latina, or Native American women. Compared to women <50 years old, women >70 years old [AOR 1.60 (95% CI 1.35-1.90)] had higher odds of nodal positivity. Compared to women with HR+/HER2- disease, women with TNBC [AOR=0.40 (95% CI 0.31-0.53)], with triple positive breast cancer [OR 0.23 (95% CI 0.19-0.29)], and with HR-/HER2+ [AOR=0.38, (95% CI=0.30-0.50) all had lower likelihoods of nodal disease. Women with invasive lobular disease had a higher likelihood of pN+ disease compared to women with invasive ductal disease [OR 1.64 (1.39-1.93)]. Women with significant comorbidities also had higher odds of node-positivity (Charlson-Deyo scores of 2+ [OR 1.41 (95% CI 1.12-1.76]). Over 90% of patients with clinically node negative, microinvasive and T1a breast cancer remain pathologically node negative following axillary staging. However, higher rates of nodal disease were found among patients with older age, Black race, lobular histology, and significant comorbidities. The consideration of axillary staging in these patients should be patient-centric and value-based.


This thesis is restricted to Yale network users only. It will be made publicly available on 04/30/2025