Metastatic breast cancer to thyroid gland: Case report

Introduction: 1.4–3% of malignant solid tumors metastases to the thyroid gland and these events are rare. When metastatic cancers present to thyroid gland, ultrasound images mimic of the thyroid parenchyma, and diagnosis is difficult. Breast cancer rarely metastasizes to the thyroid gland. Case: A 48-year-old woman was referred to endocrinologist clinic for enlargement of thyroid gland (goiter) with breast cancer history. Physical examination show multinodular goiter .Lymph nodes of cervical region were enlarged. Thyroid ultrasound (US) showed a multinodular goiter with maximum nodule size of 4 cm at the right thyroid lobe. This nodule was isoechoic and cystic degeneration areas with few coarse calcifications. There was a hypoechoic nodule up to 20 mm in left lobe, without any enlarged lymph nodes in the left cervical region. Thyroid and parathyroid hormone levels were normal. Cervical CT scan showed an enlarged thyroid gland and lymph nodes. An US-guided FNA was performed at the largest right and left thyroid lobe nodules, showed thyroid malignancy (Bethesda IV). The patient was monitored by US and thyroid hormone testing. Total thyroidectomy was performed. Histopathological examination revealed the presence of neoplastic infiltration of the right and left lobes with morphological and immunohystologica characteristics compatible with breast tissue origin: CK7 focally positive, CK20(-), TTFI(-)GATA-3(+),GCDFP15(-),Mammaglobin (-)PAX 8 (-),Chromogranin (-),Ki67 (15-20),ER (+),PR (+) Her -2 (-) . Conclusion: Metastases should be rolled out in a patient with breast cancer history and thyroid gland enlargement. FNA had been performed in the larger and calcified nodule that had the most suspicious. After total thyroidectomy, primary or secondary thyroid cancer could be diagnosed according to permanent pathology and immunohistolog findings.