Breast Carcinoma Metastasis to Thyroid Gland Masquerading as Nodular Goitre: A Case Report

Thyroid gland, despite being a highly vascular organ, is an extremely unusual site for metastasis from primary carcinoma like breast. We, hereby, report a case of metastatic lesion in the thyroid with breast carcinoma as a primary, in a 55-year-old postmenopausal female. The metastatic focus had masqueraded as nodular goitre, thereby, creating diagnostic difficulty. The case was suspected on Fine Needle Aspiration (FNA) and confirmed by immunocytochemistry on cell block with progesterone and Her2neu positivity. Also, we have attempted to review the literature reporting similar occurrences. Although breast cancer is less frequent to metastasize to thyroid, it is advised to always exclude metastasis from breast carcinoma especially if new thyroid lesions occur in patients with this malignancy. Such cases create diagnostic dilemma on cytology due to morphologic similarities between primary and metastatic thyroid lesions. Cell block is a crucial technique where ancillary techniques like immunocytochemistry can be applied and help in early and timely diagnosis, hence, rendering better prognostic outcome.