Operable early stage breast cancer patients staged according to NCCN guidelines are subjected to bone marrow aspiration/trephine biopsy at the time of the definitive operation under general anesthesia. The specimen will be fixated in neutral tamponaded formalin and the sections will be examined by H&E and cytokeratin immunohistochemically. If disseminated tumor cells are identified ER (estrogen receptor), PR (progesterone receptor), HER2/neu will be studied. Disseminated tumor cells will be recorded quantitively and semiquantitatively. Results of the pilot study will be evaluated as observational study.

Inclusion criteria:

1. Patients over 18 years old and who have given informed consent to enter the study.
2. ASA I-II patients
3. Patients who have not been diagnosed as breast cancer or received any type of treatment regarding breast cancer before the time of study
4. Patients who are appropriate for bone marrow biopsy
5. Menopausal status is not relevant.

Exclusion criteria:

1. Active collagen tissue disorders
2. Patients who are diagnosed having breast cancer and received any type of treatment regarding breast cancer before the time of study
3. Pregnancy
4. Patients with bleeding disorders, who are receiving antiaggregant or anticoagulant medication.
5. Patients who refused to enter the study protocol and refused to give informed consent.