7024 Papillary Thyroid cancer in rare cystic form

Abstract Disclosure: G. Shrestha: None. F. Qureshi: None. K. Yadav: None. S. Shrestha: None. S. Sapkota: None. M. Yadav: None. Background: Thyroid nodules are often asymptomatic and usually discovered incidentally. Thyroid cancer is found in about 8 % of nodules in men and 4 % of nodules in women. Papillary thyroid cancer is a predominant form of thyroid malignancy, accounting for almost 85 % of all cases. Papillary thyroid carcinoma usually presents as solid irregular thyroid nodules but in very rare cases it can present as a cystic variant, usually accounts for less than 10% of all cases. Although most of the thyroid cysts are considered benign, it does have less than 5% risk of malignancy. Case report:A 36-year-old female presented with a right-side neck mass for 10 years. She noticed the mass about 5 months prior to initial presentation. The exam at that time revealed a 4 cm right-sided firm, fluctuating mass that moved with swallowing. She did not pursue any investigation at the time and failed to follow up. However, she presented again with the same complaint without other systemic and local symptoms one and half years ago. Bedside ultrasound confirmed cystic thyroid nodules and she underwent ultrasound-guided FNAC with aspiration of 10ml serous fluid. FNAC was negative for malignancy, and she was advised to follow up after 4 months. Her mass initially regressed after aspiration, but it reappeared in 3-4 months. Ultrasound-guided FNAC was repeated which again did not reveal malignancy. Laboratory investigation done before the 1st FNAC procedure showed normal TSH 3.64 (0.30- 5.33 ) and normal FT4 0.86 ( 0.60-1.40 ). She was advised to see an endocrinology surgeon for surgical options because of large and recurrent thyroid cyst. After extensive discussion and given 2nd-degree family history of thyroid carcinoma (maternal uncle), she was advised to go for a right-sided thyroid lobectomy. Post-lobectomy pathology revealed a 4cm encapsulated solid/trabecular variant of Papillary thyroid carcinoma with 1mm secondary focus and strong positivity for TTF-1 and PAX-8 immunohistochemistry. Because of the finding of Papillary thyroid carcinoma, it was recommended to obtain an ultrasound soft tissue of the neck which showed suspicious lymph nodes on both the right and left side. She underwent total thyroidectomy of the remaining thyroid along with an excisional biopsy of lymph nodes that did not show malignant features. She did not have complications like dysphagia, or hoarseness following surgery. She developed post-surgical hypothyroidism after a certain period and currently, she is on levothyroxine 150mcg daily. Conclusion: Cystic thyroid nodules must not be overlooked especially if the cystic nodules are larger in size and recurrent in nature. Our case illustrates to not rely solely on FNAC if the thyroid cyst is large and recurrent after aspiration and consider the removal of the cyst along with lobectomy of the involved lobe for definite diagnosis. Presentation: 6/1/2024