To address the challenges of isolating and analyzing rare cells, this study aims to validate technical diagnostic instrumentation, tests, protocols and analysis to correlate the number of circulating tumor cells present in whole blood for predicting cancer prognosis and treatment efficacy. Investigators propose to enroll and follow cohorts of cancer patients. Blood samples will be collected from these patients at regular intervals as determined by their doctors. The patient's disease progression will be monitored over the lifetime of this study. The specific aims are to isolate, enumerate and analyze the number of circulating tumor cells (CTCs) in patient blood using chip-based sorting, filtration and imaging techniques. Investigators will also use this study to optimize diagnostic instrumentation, test protocols and downstream CTC analysis. Investigators may also correlate the results of these tests with the prognosis of the patients as well as any clinical evidence (e.g. from radiological imaging scans). While investigators focus on prognosis in this study, these correlated tests potentially may also be valuable in future studies for early diagnosis and monitoring of cancer.

Inclusion Criteria:

For inclusion in the first stage of the study, subjects must fulfill all of the following criteria:

1. Provision of signed written informed consent before enrollment into the study, ability to communicate with the investigators, and to understand and comply with the requirements of the study.
2. Patients diagnosed with stage 4 breast cancer or other types of cancer or chosen to be part of one of the negative control population cohorts.

For inclusion in the second stage of the study, subjects must fulfill all of the following criteria:

1. Provision of signed written informed consent before enrollment into the study, ability to communicate with the investigators, and to understand and comply with the requirements of the study.
2. Patients diagnosed with breast cancer or other types of cancer or chosen to be part of one of the negative control population cohorts.

Exclusion Criteria:

The following is regarded as a criterion for exclusion from the study and applicable to both 2 stages :

1. Subject has received any investigational agent within 28 days or 5 half-lives, whichever is longer, prior to the study.

healthy volunteers and breast cancer patients