Abstract

Metastases to thyroid is extremely unusual and most common primary cancer to metastasize to the thyroid is renal followed by malignancies of the gastrointestinal tract, lungs, breast and skin. Metastasis from minor salivary gland carcinoma is extremely rare with only few case reports found after extensive pubmed search. Most of the cases were found to be direct extension from tracheal or laryngeal minor salivary gland carcinoma. We present two cases of already diagnosed case of salivary gland carcinoma now presented with thyroid lesion: One is of Adenoid cystic carcinoma of Bronchus in 61 year old male diagnosed and operated in 2009, now in May 2017 he presented with nodule in upper pole of Left lobe of thyroid. On USG well defined lobulated hypoechoic lesion measuring 38 x 20 x 25 seen. Patient underwent total thyrodectomy and histomorphology and ihc profile (P63 and SMA positivity with PAX 8 and ttf1 negativity) confirm diagnosis of Adenoid Cystic carcinoma. Another case is of 45 year old male diagnosed case of Polymorphus low grade adenocarcinoma of base tongue, underwent Near total glossectomy with bilateral selective neck dissection in 2014. He presented with firm nodule in left lobe of thyroid in February 2018.On USG nodule is 18 x 13 x 15 mm heterogenous lesion with partly circumscribed and partly ill-defined margins. Patient underwent Total thyroidectomy with bilateral selective dissection and specimen showing main bulk of the tumour within left lobe of thyroid gland with minimal extra thyroidal extension. Histopathology and immunohistochemistry (CK7 and P63 positivity and PAX8 and p40 negativity) confirmed metastases to thyroid by salivary gland carcinoma.

Keywords: Salivary gland carcinoma, Thyroid metastasis, Adenoid Cystic Carcinoma (ACC), Polymorphous low grade adenocarcinoma (PLGA).