Endocrine Abstracts

Introduction: The cystic nodule is an unusual presentation of papillary thyroid carcinoma (PTC), seen in less than 10% of cases. Ultrasound discovery of a thyroid cyst represents less than 5% risk of malignancy. We report the case of a patient followed for papillary thyroid carcinoma in its cystic form.

Observation: A 42-year-old patient with no specific history. The patient underwent a right isthmolobectomy for a thyroid nodule. Anatomopathological examination of the surgical specimen revealed a thyroid cyst with endocystic vegetations of papillary appearance, totally necrotic, in favour of a papillary carcinoma in its cystic variant. Then the patient underwent a left totalization with benign histology. The postoperative course was simple. This tumor is classified as PT1aNxMx with low risk of recurrence. The patient benefited from TSH- suppressive Levothyroxine therapy, with good clinical and biological evolution.

Discussion: The malignant potential of cystic thyroid nodules should never be neglected, even if it carries a low risk of malignancy. The diagnosis of PTC in its cystic form relies primarily on typical nuclear features, however, in case of histologic uncertainty, immunohistochemical stains such as HBME-1 can be used to help classify unusual presentations of PTC. Treatment and monitoring of cystic PTC follows the conventional guideline for solid PTC.

Conclusion: Papillary thyroid carcinoma in its cystic form is rare. Our case illustrates the importance of the management of cystic thyroid nodules with an adapted follow-up in order not to ignore a malignant etiology such as papillary thyroid carcinoma.