Introduction: The role of sentinel lymph node biopsy (SLNB) when ductal carcinoma in situ with microinvasion (DCISM) is identified on core biopsy is unclear.
Objective: Our aim was to assess the upstage rate to invasive cancer and axillary lymph node metastasis in patients diagnosed with DCISM, and whether predictive variables could be identified that may help inform who would most likely benefit from a surgical axillary evaluation.
Methods: We performed a retrospective review of 70 patients diagnosed with DCISM on core biopsy. Patients with concomitant or prior invasive cancer were excluded. Demographic, clinical, radiographic, histologic, and treatment data were collected. Fisher's exact test and univariable and multivariable logistic regression were performed to identify variables that may be associated with tumor upstaging and nodal metastasis. Time-to-event distributions were summarized using the Kaplan-Meier method.
Results: On final surgical pathology, 49 patients (70%) had a final diagnosis of DCISM or T1mi cancer, whereas 21 patients (30%) were upstaged to measurable invasive cancer (> 1 mm). One of 49 patients (2%) with DCISM on final pathology and 4 of 21 patients (19%) with measurable invasive cancer showed sentinel lymph node metastases.
Conclusion: Although the upstage rate to measurable invasive cancer in our cohort of patients with DCISM on core biopsy was 30%, findings of a positive SLNB remain low at 7%. No predictive variables were identified to inform whether the routine practice of SLNB may be omitted in some patients with DCISM.