Management of Occult Breast Cancer with Axillary Involvement

Occult breast cancer (OBC), which is defined as clinically recognizable axillary metastatic carcinoma from an undetectable primary breast tumor, accounts for less than 1% of all patients who present with breast cancer (BC). Although criticized for high false positive rate (FPR) in routine BC diagnosis, the role of magnetic resonance imaging (MRI) is crucial in the diagnosis of OBC. The standard treatment for OBC, initially, was blind modified radical mastectomy, but one third of patients who undergo blind mastectomy, will have no histopathological findings of carcinoma. Current evidence supports the use of whole breast radiotherapy (WBRT) and axillary nodes clearance (ANC) as the locoregional treatment for patients with OBC. Management of the axilla does not differ from that of patients with BC with clinically palpable axillary lymph nodes (LNs) and ANC, which remains the gold standard, should be used for staging and loco-regional control. Neo-adjuvant chemotherapy (NACT) could reduce ANC by 43%, and for patients who undergo NACT with complete radiological response, a more conservative surgical approach, with a minimum of 3 sentinel lymph node biopsies (SLNBs), together with targeted dissection of the involved LNs could be considered as an option. This offers adequate staging and loco-regional control, combined with significantly less comorbidities than ANC. Overall, the prognosis of OBC is equal to or better than that of other BCs with metastasis to the axillary LNs. Progesterone receptor (PR) expression should be taken into account when evaluating the prognosis of OBC because PR-positive patients achieve better overall survival and have a lower risk of local recurrence. Surveillance should include breast MRI and mammography.