Background Tumor cells can shed from the tumor, enter the circulation and travel to distant organs, where they can seed metastases. These cells are called circulating tumor cells (CTCs). The ability of CTCs to populate distant tissues and organs has led us to believe they are the primary cause of cancer metastasis. The biological properties and interaction of CTCs with other cell types during intravasation, circulation in the bloodstream, extravasation and colonization are multifaceted and include changes of CTC phenotypes that are regulated by many signaling molecules, including cytokines and chemokines. Considering a sample is readily accessible by a simple blood draw, monitoring CTC levels in the blood has exceptional implications in oncology field. A method called the liquid biopsy allows the extraction of not only CTC, but also CTC products, such as cell free DNA (cfDNA), cell free RNA (cfRNA), microRNA (miRNA) and exosomes. Conclusions The clinical utility of CTCs and their products is increasing with advances in liquid biopsy technology. Clinical applications of liquid biopsy to detect CTCs and their products are numerous and could be used for screening of the presence of the cancer in the general population, as well as for prognostic and predictive biomarkers in cancer patients. With the development of better CTC isolation technologies and clinical testing in large prospective trials, increasing clinical utility of CTCs can be expected. The understanding of their biology and interactions with other cell types, particularly with those of the immune system and the rise of immunotherapy also hold great promise for novel therapeutic possibilities.

Background: Leukocytoclastic vasculitis may be secondary to medications, underlying infection, collagen-vascular disorders, or malignancy. We report the second case of leukocytoclastic vasculitis related to exemestane/ everolimus therapy in breast cancer and present our review of literature.Case presentation: A 68-year-old Caucasian woman, treated with exemestane and everolimus for metastatic breast cancer presented with skin necrosis and allodynia in the right mammary region. A biopsy disclosed leukocytoclastic vasculitis. The patient received radiation therapy to the right breast due to exulcerated breast cancer (20 × 2.5 Gy, total dose 50 Gy) two and a half years ago. Skin necrosis appeared after five days of treatment with everolimus and 22 days of exemestane. The treatment with exemestane was continued, but everolimus was discontinued. Allodynia disappeared in two weeks after everolimus discontinuation. The skin healed very slowly and an eschar persisted for several months. The prompt resolution of allodynia, evident healing of skin necrosis after everolimus discontinuation, and high score in the Naranjo Adverse Drug Reaction Probability Scale strongly suggest the causative role of everolimus in leukocytoclastic vasculitis.A review of literature revealed only one case of leukocytoclastic vasculitis caused by everolimus and one case of radiation recall dermatitis caused by exemestane/ everolimus. Even though it is a serious adverse effect, it is usually reversible by drug discontinuation and symptomatic treatment only. Conclusion:Everolimus-related skin recall presented as leukocytoclastic vasculitis is a very rare adverse drug reaction.

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