Circulating cancer cells in division in an early breast cancer patient.

A 63-year-old woman came for management of a second breast cancer (BC). Ten years earlier, she had a lumpectomy and axillary lymph node dissection for invasive ductal carcinoma (pT1cN0M0). The tumor cells expressed estrogen receptor (ER) and progesterone receptor (PR) and did not overexpress human epidermal growth factor receptor 2 (ERBB2). After discussion of the risks and the benefits of adjuvant therapy, the patient declined further treatment. In July 2009, a follow-up mammography revealed an architectural distortion in the upper outer quadrant. Specimens from a stereotactically guided core biopsy revealed an invasive lobular carcinoma. Lumpectomy and sentinel lymph node biopsy was carried out. This patient’s tumor was pT1bN0M0, ER positive, PR positive, and ERBB2 negative. Adjuvant treatment with aromatase inhibitors was recommended and she elected to proceed with letrozole. The patient was treated with radiation therapy to the right breast. She discontinued the adjuvant treatment due to clinically relevant musculoskeletal symptoms in March 2010. Approximately 20 months after the diagnosis of the second tumor, she had no evidence of recurrent BC. From March 2009 to September 2010, as a part of a protocol approved by the institutional review board, 98 nonmetastatic BC patients donated 10 ml of blood for the analysis of circulating tumor cells (CTCs). Samples were processed according to the protocol established for our group [1]. In brief, CTCs were captured from the peripheral blood by pan-cytokeratin (CK) 7/8 antibody-bearing ferrofluid and subsequently MACs MS columns were used for cell immunoselection. CTCs were identified by an immunocytochemical method and visualized under a direct light microscope to perform the cytomorphologic and immunophenotypic evaluation of CTC [2] (Figure 1—Legend). In this patient, positive CTCs were detected in the blood samples obtainedbefore the initiationof endocrine therapy andon 3 and 12months followup visit. Themost unexpected observation was the finding of cytomorphological features suggesting that a CTC was undergoing cell division among the five CK-positive cells detected in the last sample. Using an antibody that recognizes phosphorylated Histone 3 on Ser 10 (phosphor-H3) that is involved in the mitotic process [3], we confirmed our suspicion. There was a fluorescent signal of phospho-H3 in the separating chromosomes in one CTC that was previously identified as a CK-positive CTC (Figure 1—Legend). To the best of our knowledge, this is the first report of a CTC in division in the peripheral blood of a BC patient. Although CTCs are not usually considered in making decisions about adjuvant treatment in early BC patients, the detection of CTC in division raises an issue in the management of these patients. A possible role of the cessation of endocrine therapy and the detection of a mitotic CTC may not be ruled out; however, no reports of a similar nature are available regarding this phenomenon. Another explanation for this finding lies in the role of therapy resistance and minimal residual disease is thought to result from drug-induced molecular changes in CTCs, reflecting clonal selection during treatment [4]. CTCs have been detected in BC patients many years after diagnosis who are clinically disease free, suggesting that tumor cells are in a state of dynamic dormancy. Clinical dormancy is reflected by relapses at distant organs, following the primary cancer diagnosis. However, the mechanism of outgrowth and replacement of dormant tumor cells over time remain in question. Although we recognize that a follow-up of 20 months is a rather short time and we cannot rule out that the CTC came from the first breast cancer; we propose that the dormant CTCs turnover may be consistent with a model of homeostasis involving CTCs with self-renewing properties. There is not much individual information about the features of CTCs that can predict whether or not patients will develop a late recurrence or should expect the induction of CTCs death [5]. Further characterization of such precursors of metastasis may provide powerful translational tools to improve the clinical outcome of BC patients.