Primary Squamous Cell Carcinoma of Trachea Arising 4 Years After Radioiodine Treatment of Papillary Carcinoma of Thyroid

Primary squamous cell carcinoma (SCC) of the trachea is rare. Here, we presented a rare case of primary SCC of the trachea arising 4 years after radioiodine (RAI) treatment of papillary carcinoma of the thyroid. In this case, concomitant uptake of I-RAI and F-FDG was demonstrated in the thyroidal mass with tracheal invasion, which mimicked mixed well-differentiated and dedifferentiated thyroid carcinoma. The diagnosis of SCC of the trachea was made only after tracheal biopsy. This case illustrates that FDG-avid thyroid bed lesion, in the presence of thyroid carcinoma, may not necessarily be related to the thyroid pathology.