Pure Mucinous Breast Carcinoma With a Favorable Tumor Biology and Clinical Outcomes.

Objective: A few studies suggest that mucinous breast carcinoma (MBC) is a rare breast carcinoma with good prognostic features. Therefore, the aim of this study was to evaluate biological features and clinicopathological characteristics of pure mucinous breast carcinoma (PMBC) to determine clinical outcome in PMBC.

Materials and methods: The data of 87 patients diagnosed with PMBC between November 2004 and February 2022 were retrospectively analyzed in terms of clinicopathological and demographic characteristics, management, and outcome.

Results: The majority of the patients in this study were female, with a median (range) age of 63 (28-90) years. Out of 87 patients, 60 had breast conserving surgery, 27 had a mastectomy, 58 had sentinel lymph node biopsy (SLNB), and 24 had axillary dissection due to a positive SLNB or clinical axilla. Due to age and comorbidities, five patients were not suitable for axillary surgery. The median largest tumor diameter was 23 (5-100) mm. Only 23 patients (26.4%) received adjuvant chemotherapy, whereas almost all patients received hormone therapy. The median duration of follow-up was 53 (6-207) months. There was no local or systemic recurrence in any of the patients. Only 10 patients (11.5%) died from non-cancer causes during the follow-up and treatment period. In this study, tumor diameter was significantly higher in grade II/III tumors (p = 0.039) and in patients under the age of 50 (p = 0.027). Furthermore, lymph node metastasis was statistically significantly more likely in patients under the age of 50 (60% versus 40%, p = 0.013). Patients who had not received chemotherapy or radiotherapy tended to be older than 50 years (p = 0.002).

Conclusion: In this study, the majority of patients were in the luminal subgroups with excellent prognosis and low incidences of lymph node metastasis. As a result, PMBC has favorable tumor biology. We believe that minimal axillary surgery would be the most appropriate approach during patient treatment, due to the low rate of lymph node involvement and favorable prognosis in PMBC patients.