Immunohistochemically defined subtypes and outcome in occult breast carcinoma with axillary presentation

The aim of this study is to evaluate the outcome of occult breast cancer (OBC) in patients with axillary presentation overall and according to the immunohistochemically defined tumour subtypes. We reviewed information on 15,490 consecutive primary breast cancer patients, who underwent surgery at the European institute of oncology between September 1997 and December 2008. Patients with OBC were compared with an equal number of patients with small invasive breast carcinomas (pT1) observed at the same institution during the same period, matched for year of surgery, age, nodal status and biological features. Eighty patients with OBC (study group) and 80 patients with early breast cancer (control group) were identified. There was no significant difference in the disease-free survival (5 years DFS 66 vs. 68% P = 0.91) and the overall survival (5 years OS 80 and 86% P = 0.99) between the OBC and control groups. A statistically significant worse outcome was observed within the group of OBC for patients with more than four involved lymph nodes and with triple negative tumours. The outcome of OBC patients is comparable with that of matched patients with small sized breast cancer. High risk of relapse and death was observed in OBC patients with triple negative tumours and extensive nodal involvement.