Is thyroid gland only a "land" for primary malignancies? Role of morphology and immunocytochemistry

Background: Thyroid Metastases (TM) represent a rare entity with an estimated variability ranging between 0 and 24%. Fine needle aspiration cytology (FNAC) might be useful in discriminating between primary and TM nodules especially when ancillary techniques (i.e.; immunocytochemistry-ICC) are carried out. Methods: We herein appraised a series of 20 TM on FNAC analyzed between 2000 and 2013. We included eight male and 12 female patients. The cytological cases were processed with both liquid based (LBC) and conventional cytology. Results We reported 2.2% TM out of 910 malignancies. Our TM cases resulted as: six lung (LG), five gastro-intestinal (GI), five breast (B), three larynx (LX), and one clear cell renal carcinoma (CCRC) metastases. All the patients had a previous known cancer history. Although the cytological features were likely to suspect a TM, the application of ICC panels was contributive in 100% cases. None of TMs resulted as a unique localization whereby two cases underwent total thyroidectomy (including one B and one CCRC) and 18 TM were treated with radio-chemotherapy approaches. Conclusions; FNAC empowered the diagnostic workup of patients with TM avoiding useless surgical approach. The low sensitivity of cytology might be reinforced by the application of ancillary techniques. In contrast with the reported predominant rate of kidney metastatic carcinomas, our findings underlined that intestinal cancer as well as lung and breast are the most common TM. TM are frequently multifocal and in a contest of a systemic disease so that a tailored therapy seems to be the best treatment