SAT-363 - A Rare Presentation of Papillary Thyroid Microcarcinoma with Contralateral Lymph Node Metastases Following Benign Cytology of A Lateral Neck Mass

Background: Papillary thyroid cancer (PTC) typically presents as one or more discrete thyroid nodules in most cases found incidentally by imaging or by physical exam. Most of these nodules meet criteria for FNA biopsy based on size and sonographic features. As per ATA guidelines, FNA is not recommended on nodules less than 1 cm. It is rare for PTC to present with metastasis in a sub-centimeter primary tumor. Here we present such a case.

Case: We present a 55 year old male with a chief complaint of right neck mass. He was referred to ENT after evaluation for right shoulder pain which led to physical exam finding of a lateral right neck mass. Follow up CT of the neck and soft tissues revealed inferior and superior lateral right neck masses with non-specific characteristics.
ENT performed FNA of the superior mass with thyroglobulin washout. Cytology resulted as scant cellularity with macrophages without signs of malignancy. Thyroglobulin washout was markedly elevated. Neck ultrasound found two circumscribed lateral right neck masses and right thyroid lobe with unremarkable/benign findings.
ENT performed total thyroidectomy with bilateral neck dissection given the high level of thyroglobulin from FNA of the mass.
Final pathology revealed a single 3 mm classic PTC of the left thyroid lobe with no angioinvasion, no extrathyroidal extension and all margins negative for carcinoma. Mitotic rate was less than 3 mitoses per 2mm2. One pre-tracheal and seven contralateral lymph nodes were found positive with PTC largest 1.9 cm including right level 2,3 and 6. The patient received RAI with I-131 following surgery.
Discussion/

Conclusion: In PTC, contralateral lymph node metastasis without ipsilateral metastasis is not common, especially in microcarcinoma, without other high risk features in the pathology. Per recent ATA guidelines, it is not recommended to biopsy nodules less than 1 cm. The most significant feature of our case is the lack of an intrathyroidal malignancy that would meet current criteria for FNA yet it developed into metastatic PTC to contralateral lymph nodes with few independent risk factors. This case serves as a stark reminder that thyroidologists must stay vigilant if clinical suspicion for malignancy is high despite normal or benign findings in typical diagnostic modalities . In this case, the utility of thyroglobulin washout in detecting occult cases of metastatic PTC was well demonstrated considering inconclusive image findings and benign cytology results. In conclusion, our case serves as a reminder that all forms of diagnostic modality should be exercised and exhausted when clinical suspicion for a malignancy of the thyroid is high in palpable neck masses.

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