Background: The unpredictability of thyroid cancer can be striking, as the disease may rapidly progress to death in some individuals. Herein, we reported a rare case of aggressive papillary thyroid cell carcinoma (PTC) in an elderly patient de-differentiated into squamous cell carcinoma (SCC).
Clinical Case: We describe a case of a 79-year-old Thai woman with a history of papillary thyroid carcinoma at right side of thyroid 3 years ago. The patient underwent total thyroidectomy at the initial hospital and received a high dose of radioactive iodine treatment at our hospital 1 month following the surgery and then lost to follow-up. Two years later she came back again with new development of right solid-cystic neck mass which was found to be recurrent PTC. Radical neck dissection was done and the second high dose of radioactive iodine treatment was given. However, she developed recurrent mass with tenderness at the site above previous solid cystic mass 6 months later. Re-exploration of neck mass revealed inflammatory midline mass 2 cm with enlargement of right lateral cervical lymph nodes. The histopathological examination of midline neck mass showed poorly differentiated SCC with lymphatic invasion. The intermingling of two morphologically distinct tumors typical PTC and poorly differentiated SCC had been identified in 1 out of 14 excised cervical lymph nodes. Immunohistochemistry revealed diffuse CK5/6, P63, and PAX8 positivity in the squamous cells suggesting a transformation process, and not a collision tumor. The patient decided to watchful waiting without further treatments. She is still in stable condition at 24 months later.
Conclusion: This case clearly demonstrated that SCC transformed from a pre-existing PTC. The clinician should consider a possible transformation of papillary thyroid cancer into more aggressive histological types in elderly patients who present with rapidly progressive clinical behavior. However, long-term survival can be expected for some patients.