Background: Adenoid cystic carcinoma of the breast (ACCB) is a rare histological subtype of breast cancer characterised by unique clinical features and management challenges. ACCB remains poorly understood, with limited data on its epidemiology, treatment outcomes and prognostic factors. This study aimed to elucidate the landscape of ACCB in a real-world context.

Methods: A retrospective cohort study was conducted on patients diagnosed with ACCB in a Brazilian cancer center between January 2007 and October 2021. Clinical and pathological data were systematically collected from electronic medical records. Statistical analyses were performed to identify factors associated with prognosis and assess the impact of treatment interventions.

Results: Twenty-one female patients with confirmed ACCB were included in the study. The median age at diagnosis was 55.2 years. Most patients had basaloid (38.1%) or classic (19.0%) histological subtypes. Adjuvant radiotherapy was associated with a trend towards better recurrence-free survival among patients with localised disease HR 0.21, CI 95% 0.04–1.06, p = 0.059). In the metastatic setting, systemic chemotherapy used for breast cancer demonstrated limited efficacy, with a median progression-free survival of 1.8 to 2.8 months. Despite the overall poor prognosis, two patients with low-volume metastatic disease had long-term survival following local therapy.

Conclusion: Given the rarity of ACCB and the absence of a standard management approach, this small study suggests a potential benefit of local therapies in adjuvant and metastatic settings while indicating the limited efficacy of systemic chemotherapy. Personalised treatment strategies tailored to ACCB are essential to optimising patient outcomes.