Endocrine Abstracts

Background: Basal tumor markers are valuable in preoperative evaluation of medullary thyroid carcinoma (Calcitonin and CEA), but are insensitive and nonspecific for papilary thyroid cancer (thyroglobulin). Even if their utility is questionable or not recomended in the evaluation of thyroid nodules, in some cases refered to endocrinology department they are available and can be misleading. We present two cases of thyroid nodules with very high preoperative tumor markers.

Case 1: A 67-years old man, with history of hepatocellular carcinoma, had a markedly elevated CEA (188ng/ml; reference range <6.5ng/ml), without an evident diagnose. The calcitonin was measured and the result was 8024ng/l (<14,3ng/l). The patient was referred to endocrinology department to further investigation. The thyroid ultrassonography showed a nodule in the right lobe with 77x52x38mm predominantly solid, mildly hypoechogenic. Fine-needle aspiration was benign, immunohistochemical staining of calcitonin and CEA negative, with high calcitonin in the washout fluid (827ng/l), but incomparably lower than serum. Due to discrepancy in the results a 68Ga-DOTANOC PET was performed with high thyroid nodule uptake (SUVmax 12.6). No locoregional lymph node or distant metastasis were identified in the CT/ultrasonography. A total thyroidectomy was performed, with histological result of medullary thyroid cancer. The calcitonin 6 monts after surgery is 2.6ng/l.

Case 2: A 48-years old women presented with a hypertensive crisis with aortic dissecation. Bone metastatis were incidentally found in CT, mainly in iliac, sternum and spine. Due to non evident primary tumor, a FDG-PET was performed with abnormal uptake in a thyroid nodule (SUVmax 26), bone lesions and also in parotid gland. Thyroid function and serum thyroglobulin (Tg) levels were prescribed and the patient was referred to endocrinology department. The thyroid ultrassonography showed a 30x26x47mm predominantly solid, mildly hypoechogenic, without any suspicious lymph node. Fine-needle aspiration was non-diagnostic. Thyroid function was normal (TSH 2,17mUI/l), but Tg levels were very high (15362 mg/l; reference <77 mg/l). The bone lesions biopsy was compatible with adenocarcinoma, without expression of TTF1, PAX8 or Tg. The patient died due to disseminated intravascular coagulation, and primary tumor was not found in autopsy.

Discussion: Thyroid tumor markers are helpful in postoperative evaluation. Calcitonin is an important marker preoperatively in medullary thyroid carcinoma. However, a very high level as presented in our case isn’t pathognomonic of distant metastasis. Preoperative serum Tg levels are nonspecific and can be misleading in cases of distant metastasis without evident primary tumor, as presented in our second case.