Case Presentation: A 68-year-old woman presented with a small, right-sided neck lump, without any compressive symptoms. She reported the size of the lump had been constant for 7 years and denied hyper or hypothyroidism symptoms. No known family history of thyroid, pheochromocytoma or calcium disorder was noted. Past medical history showed hypertension.Her neck examination showed a small palpable hard nodule on the right lobe of the thyroid, which moved with deglutition. There were no signs of hyper- or hypothyroidism. The review of her systems was normal. Because of cancer concern, thyroid USGs, routine thyroid function tests, calcitonin, CEA and four FNA biopsies were carried out in last 7 years. Her first three FNA biopsies showed scant chronic lymphocytic thyroiditis with some atypical cells of uncertain clinical significance together with borderline high calcitonin and CEA levels.Her last FNA showed atypical cells of follicular neoplasm with positive calcitonin stain indicating medullary thyroid carcinoma(MTC). Her thyroid USGs showed a hypo-echoic roundish 9.2*7.9*8.4 mm nodule with central shadowing calcifications of the right lobe. There were no increased parenchymal vascularity and no cervical lymphadenopathy. Her CT (chest and abdomen) and MRI (brain) done after her fourth FNA biopsy revealed a 5 mm contrast-enhanced nodule in the right thyroid lobe with conspicuous enlargement of the level 1 & 2 lymph nodes bilaterally on STIR imaging.She was explained about the possibility of MEN-2 syndrome and further diagnostic evaluations such as calcitonin, CEA, calcium, PTH(intact), vitamin D, and thyroid function test. She was referred to a genetic counselor for RET gene mutation test & counseling as well as to an ENT surgeon for evaluation of further management.Total thyroidectomy was done and pathologic diagnosis confirmed 0.8cm microcarcinoma of the right lobe. Positive synaptophysin and TTF-1 stains support the diagnosis of MTC. On follow-up visit, calcitonin and CEA levels returned to normal range and the patient was clinically euthyroid on levothyroxine supplementation.
Discussion: Generally, microcarcinoma of the thyroid is defined as cancer 10mm or less in maximal size [1-2]. 35% of all MTC patients with palpable neck lump present with regional metastasis and 13% with distant metastasis. And, the mean tumor size is 2.8cm with a standard deviation of 2.4. Overall survival after diagnosis differs according to tumor stage. Patients with locally invasive tumors have an excellent prognosis and a ten-year survival rate of more than 95%. In contrast, patients with distant metastasis have poor prognoses with a ten-year survival rate as low as 40% [3]. In one study, the size of a thyroid nodule and the malignancy risk are inversely related to each other[4]. Actually, the clinical significance of the microcarcinoma of MTC (microMTC) is not well-established and the largest data that have been reported so far were from the post-mortem autopsy findings [5].
Conclusions: MicroMTC was diagnosed in this woman with no hypercalcemia or pheochromocytoma. We did the biomarkers such as calcitonin, and CEA together with tests for ruling out the possibility of MEN-2 syndrome. Although there are numerous debates about the microMTC management, post-operative calcitonin level and CEA levels are of interest to measure postoperatively to assess the disease progression and prognosis [6]. It also underscores the clinical significance of microMTC for the development of the clinical guideline as a different entity in the future.
