AB218. SOH26AB_0172. Ductal carcinoma in situ (DCIS) and microinvasion: can we de-escalate?

Background: With the rise of mammographic screening, diagnoses of ductal carcinoma in situ (DCIS) and microinvasive breast cancer have become increasingly common. Surgery continues to play a central role in treating these conditions. This is a retrospective study aiming to know the role of sentinel node biopsy is DCIS with microinvasion and centres on the de-escalation of surgical intervention in managing these patients.

Methods: Central pathology retrospective evaluation of data was performed for patients with a diagnosis of DCIS and microinvasion enrolled from January 2024 to December 2024. Demographics of patients were collected, with tumour size, grade, sentinel node positivity, microinvasion on final histology specimen, and presence of lymphovascular invasion (LVI).

Results: Of 19 patients diagnosed with microinvasion on core biopsy, all underwent sentinel lymph node biopsy. Sentinel nodes were negative in 100% of cases. Mean age found in patients was 58 years. Mean tumour size was 38.29 mm, tumour grade was high in 57.9% (11/19), intermediate grade in 42.1% (8/19). Most of the DCIS were in the mixed category, and only one patient had only cribriform type. LVI was positive in 15.8% (3/19). 68.4% (13/19) of patients underwent wide local excision, and 31.6% (6/19) had mastectomy.

Conclusions: Although this sample size is small and limits the strength of any conclusions, continued data collection may provide valuable insight into whether axillary management can be safely de-escalated in microinvasive disease in DCIS. (data collection in progress)

Keywords: Breast cancer; ductal carcinoma in situ (DCIS); de-escalation; microinvasion; sentinel node biopsy