Occult breast cancer (OBC) accounts for 0.3-1.0% of all breast cancers and is a rare presentation of the disease. The present retrospective study examined the overall survival and prognostic factors associated with OBC in Korea.

The study included 142 OBC patients identified from the Korean Breast Cancer Society cancer registry from January 1990 to December 2009. All patients had pathologically positive axillary lymph nodes (N1-N3) and pathologically and radiologically negative in-breast lesions (T0/Tx) based on a retrospective review of the database.

No statistically significant differences in overall survival were observed between patients undergoing axillary lymph node dissection (ALND) only (80.8%), breast conserving surgery (BCS) with ALND (98.0%), and mastectomy with ALND (92.5%) with P-value of 0.061. Nodal status was a significant prognostic factor (P = 0.004) on univariate analysis. When compared with T1 patients group, T0/TxN1 patients showed better survival than T1N1 patients (hazard ratio [HR] 0.253; 95% confidence interval, 0.104-0.618; P = 0.003), but T0/TxN2, T0/TxN3 patients showed similar survival to T1N2, T1N3 patients.

OBC patients treated with ALND only showed comparable outcomes to those undergoing ALND combined with BCS or mastectomy. Nodal status may be an independent predictor of poor outcome in OBC patients.