This is a Prospective Clinical Trial without drugs, to determine the HER2 status in the metastasis of patients with primary breast cancer HER2. 32 Sites have been taking part in this Clinical Trial.

Population definition: Women previously diagnosed with a primary breast carcinoma who present locally recurrent or metastatic lesions and who meet the selection criteria. The expected sample size is 175 patients.

Observation period: Each patient in the study will be observed from their inclusion in the study until 1 year after the inclusion of the last patient in the study. These visits will match with the scheduled follow-up visits made by the patient according to the usual clinical practice of the site.

Determination of sample size: The calculation of the sample size will be based on determining a number of patients that will achieve the main objective of the study.

The fulfillment of the secondary objectives of the study will be obtained from the size determined by the main objective.

Main objective of the study is to: Prospectively determine the probability of conversion of the HER2 stage between the different subtypes of primary breast cancer (luminal, triple negative and HER2) and their respective metastases.

A review of the literature has allowed to find several published works with varying percentages of HER2 disagreements determined by IHQ + FISH or FISH, which have allowed to estimate an average percentage of disagreements of 10.45% (range between 4% and 20%). Considering the hypothesis that the level of disagreement in each of the different subtypes of primary, luminal, triple negative and HER2 breast cancer, is presented in an approximately similar frequency, that is to say approximately 10.45%.

From the aforementioned data, an average conversion rate to be expected of 10% will be assumed. An alpha risk of 0.05 will be accepted, with an accuracy of +/- 0.09 percentage units, with a bilateral contrast, for which it would be necessary to include 43 patients for each of the three groups mentioned above (luminal, triple negative and HER2), which consequently includes 129 patients. If a loss rate is assumed (patients registered with biopsies finally not performed or not valid, or with inconclusive results or reflecting other diagnoses) of approximately 25%, the necessary size would increase to a total of 172 patients.

Based on these calculations, the final sample size would be 175 patients

Inclusion Criteria:

• Patients who have given their written informed consent to participate in the study.
• Women over 18 years.
• Breast cancer locally recurrent or metastatic at first relapse or after successive progressions.
• Patient has to have available a sample of the primary tumor in paraffin.
• Patients who are planning for the next 6 weeks, the biopsy (fine needle aspiration / drainage of fluid cavities, open biopsy, core biopsy) of locally recurrent or metastatic lesion [local relapse in the chest wall, nodal , cutaneous or subcutaneous metastases, peripheral lymph nodes and other soft tissues accessible, bone metastases, visceral metastases (lung, liver, brain, etc..) or pleural effusion / ascites / pericardial / cerebrospinal] according to clinical practice center.

Exclusion Criteria:

• Patients with cognitive impairment that might impede a proper understanding of the written informed consent, according to medical criteria.
• Ipsilateral breast local relapses or contralateral breast away.
• Patients diagnosed with a second neoplasm, with the exception of cervical carcinoma in situ and non-melanoma skin carcinoma treated properly.

Female patients diagnosed of primary breast carcinoma with locally recurrent breast carcinoma or metastasic