Pathologic fracture of the femur neck as first manifestation of a minute columnar cell carcinoma of the thyroid gland

This case report concerns a 64 year-old woman who presented a pathologic fr acture of the femur neck. Histologic examination of the performed bone biop sy disclosed the presence of a carcinomatous metastasis with unusual micros copic features. The site of the primary tumor could be unequivocally determ ined as being the thyroid gland, as immunostaining of the tumor cells showe d positivity with anti-thyroglobulin. The thyroidectomy specimen weighed 14 9 g, was nodular and partially calcified. Exhaustive microscopic examinatio n finally revealed the presence of a minute columnar cell carcinoma, 0.6 cm in diameter, with obvious vascular invasion. This case illustrates well 1) the usefulness of immunostaining with anti-th yroglobulin in cases of bone metastasis with unusual microscopic features a nd unknown primary, as well as 2) the aggressiveness of this rare type of c arcinoma of the thyroid.