Endocrine Abstracts

Introduction: Papillary thyroid carcinoma is well known as a differentiated thyroid carcinoma with an established treatment protocol and high survival rates. Poorly differentiated thyroid carcinoma, or anaplastic, is highly aggressive, manifesting with local invasion, recurrence, and distant metastasis; it is well known that these two entities may be connected as a process of dedifferentiation, most commonly met in elderly people with a long term standing untreated well differentiated thyroid carcinoma.

Case report: We present the case of a 48 years old female, Caucasian, from an area of known iodine deficiency, non-smoker, with professional exposure to toxic substances, who was diagnosed in 2013 with toxic goiter, for which she was treated with anti-thyroid drugs. In 2016 she underwent left lobectomy, but the presence of adenopathies imposed the need of surgical reintervention a few months later – total thyroidectomy with lymphadenectomy. The histopathological diagnosis was of papillary thyroid carcinoma with lymph nodes metastases T3N1BMx. Total body RAI showed no signs of local or distant metastasis; so, radioiodine therapy (250 mCi) and suppressive levothyroxine treatment was considered fit. The patient was lost to follow-up until 2018 when she addressed to the surgical department for bilateral cervicotomy and yet again the histopatological diagnosis was of papillary thyroid carcinoma with no tumoral infiltration. Afterwards, the therapeutical approach was radioiodine therapy (400 mCi) and suppressive levothyroxine treatment. A few months later, the patient developed paracicatricial cellulitis with fistula; laboratory testing revealed mild inflammatory changes and CT scan showed fluid accumulation in the left postoperative thyroid bed and multiple necrotic adenopathies as large as 1.8/1.5 cm. Once again, surgical reintervention was needed to remove the cervical necrotic tissue and lymphadenectomy, but this time the histopathological examination stated a low differentiated thyroid carcinoma, this diagnose imposing tyrosine kinase inhibitors (TKI) as the solely therapeutic option.

Discussions: The evolution of this patient’s thyroid malignancy proved to be completely unpredictable, considering that the dedifferentiated process of the papillary thyroid carcinoma is improbable to occur in young patients and especially in a such short period of time – less than 8 months between the two different histopathological diagnosis. The biological or molecular trigger for this kind of ‘blitz’ dedifferentiation remains a question mark, therefore genetic testing might be helpful in better understanding of pathophysiology and evolution of low differentiated thyroid carcinoma.

Keywords: papillary thyroid carcinoma, dedifferentiated thyroid carcinoma