Endocrine Abstracts

Introduction: Anaplastic thyroid carcinoma (ATC) is the most aggressive and invasive histological type of thyroid carcinomas. Frequently, upon diagnosis obstructive symptoms and loco-regional metastasis have already occurred. Presence of distant metastasis in the skeletal muscle in ATC is rare; and there are less than five documented cases reported worldwide.

Case: A 68-year-old Filipino Male, presents with two-month history of pain on the right thigh. He has previous history of Papillary thyroid carcinoma and underwent total thyroidectomy with post-operative radioactive iodine treatment. He was asymptomatic until 11 months post thyroidectomy, when he complained of progressive swelling and tenderness on his right thigh. On initial consult, CT scan of the right lower extremity showed a possible angiosarcoma. Biopsy revealed undifferentiated metastatic carcinoma and immunohistochemical stain is positive for CK7, PAX 8 and TTF-1; denoting anaplastic thyroid carcinoma. Due to the findings, he eventually consulted our institution, on examination there’ notable firm non-tender mass about 4 × 4 cm at the left supraclavicular area, and erythematous 6 × 8 cm firm mass on the posteromedial aspect of the right thigh. Repeated excision biopsy of both masses was performed, during the surgery an invasion of necrotic tissue surrounding the mass was seen. Histopathology of both masses presented anaplastic tumor cells. Total hip disarticulation was done due to severe infection and tumor invasion. Further plans for chemotherapy was not executed due to severe sepsis, and eventually patient succumbed to death.

Conclusion: In patients with previous history of well differentiated thyroid carcinoma, a rapidly enlarging neck mass or even a new mass of unknown origin should be suspected for a more aggressive histologic type of thyroid cancer. Aggressive diagnosis should be immediately performed on these patients, due to the risk of de-differentiation to anaplastic thyroid carcinoma. Keen knowledge is needed for clinicians to prevent misdiagnosis and to avoid delay of treatment.