Thyroid inclusion in the lung. Metastasis of an occult papillary carcinoma or ectopia?

The incidental autopsy finding of a thyroid inclusion in the lung of a 26-year-old man, accompanied by an occult papillary carcinoma (OPC) in the thyroid gland, raises the question about the possibility of true thyroid ectopia in the lung vs. metastasis of an OPC. Based on the embryonic development of the thyroid gland and the known thyroid ectopias, as well as on statistical figures on OPCs and their metastases, both possibilities are discussed. The histological pattern of the thyroid inclusion and the lack of regional nodal metastases argue in favour of ectopia, even though a definitive conclusion cannot be drawn.