Occult breast cancer presenting as axillary lymph node metastases: a single-institution experience with a challenging diagnostic and therapeutic dilemma

Background: Occult breast cancer with axillary lymph node metastases but without evidence of primary tumor on clinical examination and conventional imaging is a rare but serious scenario. Due to diagnostic difficulties and prognostic uncertainties, evidence to guide the management of such patients is lacking. Here, we review the cases of occult breast cancer treated at our institution and discuss recent advances in its management. Methods: We searched our database for patients with occult breast cancer operated on between 2002 and 2011. The following data were extracted: clinical presentation; diagnostic work-up; surgical treatment; adjuvant management; and duration of follow-up. Results: Out of 1405 patients operated on for breast cancer, 7 (0.5%) had occult breast cancer. The mean age at diagnosis was 60.5 years. Six patients were postmenopausal. All patients had one or more metastatic axillary lymph nodes but no signs of malignancy at either conventional imaging (mammography and ultrasonography) or clinical examination. Magnetic resonance imaging revealed the primary breast tumor in 1 patient. Histopathology showed positive estrogen receptors in 3 patients. After preoperative staging, neoadjuvant chemotherapy and subsequent mastectomy was performed in 1 patient with N3 disease, primary surgical treatment in 5 patients (4 mastectomies, 1 breast-conserving procedure), and chemotherapy alone in 1 patient. Postoperative management included chemotherapy in 5 patients, endocrine therapy in 2, and radiation therapy in 5. An infiltrating carcinoma was found in 5 mastectomy specimens (4 ductal histotype and 1 lobular histotype). The mean tumor size was 11 mm (range, 7-17). At a mean follow-up of 51 months, 6 patients were disease-free, and 1 patient died of pulmonary embolism. Conclusions: Occult breast cancer poses difficult management issues, especially when estrogen receptor status is negative. No consensus exists on the need for breast surgery in such patients, as recent literature suggests that breast irradiation might be an alternative treatment. Management decisions should be taken on an individual basis with a multidisciplinary approach. Considering the results of this series, we believe that breast surgery should be proposed to patients with occult breast cancer.