Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 6 1 2021 05 15 1 5 Hedieh Moradi Tabriz Department of Pathology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Arezoo Efekhar Javadi Department of Pathology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Atieh Zandnejadi Department of Pathology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Adel Yazdankhah kenary Department of Surgery, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Reza Hajebi Department of Surgery, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. 2020 06 05 2020 08 04 Breast cancer is the most common cause of cancer death in women of middle age (20-59) through last decade. In contrast Incidence rates for thyroid cancer may have begun to stabilize in recent years. Synchronous neoplasms of both thyroid and breast cancer are very rare in clinic. The current study presents a case of synchronous papillary thyroid carcinoma and breast ductal carcinoma in 37 years old woman. It is proposed that the mechanism of these synchronous primary tumors is associated with an interaction between the breast and thyroid hormonal responses. It is important to examine breast tissue in patients with thyroid carcinoma or vice versa. In our case although axillary sentinel lymph node was free from tumor, cervical lymph nodes were involved by breast carcinoma; showing importance of cervical examination in breast cancer patients. https://crcp.tums.ac.ir/index.php/crcp/article/view/362 https://crcp.tums.ac.ir/index.php/crcp/article/download/362/388