A 36-year-old female presented with lump in the left breast of 2 months duration. Fine-needle aspiration cytology (FNAC) and trucut biopsy confirmed the diagnosis of
carcinoma. Clinically, it was T3N1Mx disease. Computed tomography (CT) of the chest detected bilateral lung
metastasis. CT head and neck detected a nodule in the thyroid which on FNAC was suspicious of
papillary carcinoma. The patient was started on
chemotherapy for
breast disease with a good initial response; however, while on-follow up, there was progression of disease at primary site. The patient was taken up for surgery.
Radical mastectomy along with total
thyroidectomy was performed. Histopathological examination showed infiltrating duct
carcinoma, not otherwise specified type and
papillary carcinoma thyroid. There was a 0.4 cm × 0.4 cm metastatic focus, from
breast carcinoma within the
papillary carcinoma thyroid. The
metastasis was confirmed by immunohistochemistry.
Metastasis to thyroid is rare. However,
tumor-to-
tumor metastasis with
papillary carcinoma serving as recipient to
breast carcinoma is exceedingly rare with very few case reports in the literature. We report this case for its rarity and also for highlighting the fact that pathologists should keep in mind the possibility of
metastasis also when coming across unusual morphology in thyroid lesions.