Occult Follicular Thyroid Carcinoma presenting as Primary Breast Tumor with Sternal and Skull Metastasis

Introduction: Follicular thyroid carcinoma (FTC) that initially presented as breast tumor with no previous medical history of malignancy of thyroid gland is relatively rare and may cause diagnostic confusion.Presentation of case: We report a 59-year-old Mexican woman with no prior history of malignant thyroid neoplasm that presents with pain and swelling in the upper outer quadrant of the left breast with a year of evolution. Subsequently, subcutaneous tumor was identified in left parietal region. Clinically it was thought in primary breast tumor metastasis to skull. Furthermore, computerized tomography scan identified a tumor in the deep portion of the left breast, infiltrating the sternum that subsequently was confirmed a follicular carcinoma of the thyroid gland.Conclusion: Metastatic FTC may mimic a primary breast tumor. The combined use of clinical information, histopathology and immunohistochemistry were important to establishing a correct cancer diagnosis