Endocrine Abstracts

Background: Medullary thyroid carcinoma (MTC) is a rare thyroid tumor (around 2% of thyroid cancers). Its prognosis is generally worse than for differentiated thyroid cancers. A very rare subset of MTC is described as encapsulated MTCs. To date, a limited number of case reports and case series have been published, and this type of tumor presents with no evidence of metastases even in case of very high levels of serum calcitonin.

Case: A 33-year old pregnant woman, diagnosed incidentally with a suspicious nodule in the right thyroid lobe (taller-than-wide, hypoechoic, well-defined, regular border). She also had slightly elevated serum calcitonin 20 pg/ml, which increased to 27 pg/ml in 4 weeks, along with slightly increased CEA 5.08 ng/ml, and FNAB was performed. The cytological result was benign (Bethesda II). She returned to our clinic at 3 months post-partum with a calcitonin level of 36 pg/ml and increased anxiety, her thyroid nodule had less suspicious appearance (wider-than-tall, more anechoic zones). She underwent a core-needle biopsy with a result suggesting a Hürthle-cell neoplasm (KTA-CNB IVc). The next step was a diagnostic right hemithyroidectomy with a pathology report suggesting a benign follicular lesion with some atypia. Hence, the IHC (immunohistochemistry) was performed and revealed a low-grade encapsulated MTC, follicular variant with Ki-67 1%, CK-19 and CD-56 positive, Thyroglobulin and Galectin-3 negative, Calcitonin, CEA, Chromogranin-A positive. Postoperatively, the patient had undetectable calcitonin, normal CEA (1.26 ng/ml), no pathological findings on neck ultrasound (no nodular lesions in her left thyroid lobe, no suspicious lymph nodes in central or lateral neck). The endocrinologist’s advice was to test for hereditary RET mutations, as well as somatic mutations and to follow up with neck ultrasound and calcitonin measurements. The surgeon advised her to opt for total thyroidectomy and the patient’s decision was to avoid any risk and undertake surgery. A contralateral lobectomy with ipsilateral lymph node dissection were performed to minimize any risk and better stage the disease. Postoperative pathology did not reveal any foci of thyroid cancer in the left lobe and no lymph node metastases.

Conclusion: This case reflects the importance of the multidisciplinary team discussion. Logistic and financial difficulties in genetic testing also contributed to patient’s decision to choose the second surgery. We probably need more data on these tumors to be able to classify them as benign (adenoma?) or very low-risk tumors which could reduce anxiety of the patients and doctors.