Cytopathology Case 1. Thyroid mass from an elderly patient.

cell block preparation:

Diagnosis: metastatic lung adenocarcinoma to thyroid

This case is challenging as the tumor cells demonstrating papillary structure, nuclear enlargement, nuclear membrane irregularity, and prominent nucleoli that mimics PTC. But these nuclei are too hyperchromatic. In addition, frequent mitotic figures are seen, which is uncommon for PTC.

Metastasis to thyroid is rare.